diff --git a/lib/main.js b/lib/main.js
index db21b85..bb6a141 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -45,9 +45,11 @@ Neo4j.prototype.insertNode = function(node, labels, callback){
 			.post(this.url + '/db/data/node')
 			.set(this.header)
 			.send(node)
-			.end(function(result){
-				if(result.body && result.body.data) {
+			.end(function(err, result){
+				if(result && result.body && result.body.data) {
 					that.addNodeId(result.body, callback);
+                } else if(err) {
+                    callback(err);
 				} else {
 					callback(new Error('Response body is empty'), null);
 				}
@@ -91,9 +93,11 @@ Neo4j.prototype.readLabels = function(node_id, callback){
 	request
 		.get(this.url + '/db/data/node/' + node_id + '/labels')
 		.set(this.header)
-		.end(function(result){
-			if(result.body) {
+		.end(function(err, result){
+			if(result && result.body) {
 				callback(null, result.body);
+            } else if(err) {
+                callback(err);
 			} else {
 				callback(new Error('Response is empty'), null);
 			}
@@ -108,20 +112,24 @@ Neo4j.prototype.deleteNode = function(node_id, callback){
 	request
 		.del(this.url + '/db/data/node/' + node_id)
 		.set(this.header)
-		.end(function(result){
-			switch(result.statusCode){
-				case 204:
-					callback(null, true); // Node was deleted.
-					break;
-				case 404:
-					callback(null, false); // Node doesn't exist.
-					break;
-				case 409:
-					callback(null, false); // Node has Relationships and cannot be deleted.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' occurred while deleting a node.'), null);
-			}
+		.end(function(err, result){
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode){
+                    case 204:
+                        callback(null, true); // Node was deleted.
+                        break;
+                    case 404:
+                        callback(null, false); // Node doesn't exist.
+                        break;
+                    case 409:
+                        callback(null, false); // Node has Relationships and cannot be deleted.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' occurred while deleting a node.'), null);
+                }
+            }
 		});
 };
 
@@ -161,17 +169,21 @@ Neo4j.prototype.readNode = function(node_id, callback) {
 	request
 		.get(this.url + '/db/data/node/' + node_id)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					that.addNodeId(result.body, callback); // Node found.
-					break;
-				case 404:
-					callback(null, false); // Node doesn't exist.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' occurred while reading a node.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        that.addNodeId(result.body, callback); // Node found.
+                        break;
+                    case 404:
+                        callback(null, false); // Node doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' occurred while reading a node.'), null);
+                }
+            }
 		});
 };
 
@@ -184,17 +196,21 @@ var replaceNodeById = function(node_id, node_data, callback) {
     .put(that.url + '/db/data/node/' + node_id + '/properties')
 	.set(this.header)
     .send(that.stringifyValueObjects(that.replaceNullWithString(node_data)))
-		.end(function(result) {
-      switch(result.statusCode) {
-        case 204:
-          callback(null, true);
-          break;
-        case 404:
-          callback(null, false);
-          break;
-        default:
-          callback(new Error('HTTP Error ' + result.statusCode + ' when updating a Node.'), null);
-      }
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 204:
+                        callback(null, true);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when updating a Node.'), null);
+                }
+            }
     });
 };
 // Create an alias
@@ -277,20 +293,24 @@ Neo4j.prototype.insertRelationship = function(root_node_id, other_node_id, relat
 			type: relationship_type,
 			data: that.stringifyValueObjects(that.replaceNullWithString(relationship_data))
 		})
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 201:
-					that.addRelationshipId(result.body, callback);
-					break;
-				case 400: // Endnode not found exception
-					callback(null, false);
-					break;
-				case 404: // Startnode not found exception
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when inserting a Relationship.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 201:
+                        that.addRelationshipId(result.body, callback);
+                        break;
+                    case 400: // Endnode not found exception
+                        callback(null, false);
+                        break;
+                    case 404: // Startnode not found exception
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when inserting a Relationship.'), null);
+                }
+            }
 		});
 };
 
@@ -301,17 +321,21 @@ Neo4j.prototype.deleteRelationship = function(relationship_id, callback) {
 	request
 		.del(that.url + '/db/data/relationship/' + relationship_id)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 204:
-					callback(null, true);
-					break;
-				case 404: // Relationship with that id doesn't exist.
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when deleting a Relationship.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 204:
+                        callback(null, true);
+                        break;
+                    case 404: // Relationship with that id doesn't exist.
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when deleting a Relationship.'), null);
+                }
+            }
 		});
 };
 
@@ -323,17 +347,21 @@ Neo4j.prototype.readRelationship = function(relationship_id, callback) {
 	request
 		.get(that.url + '/db/data/relationship/' + relationship_id)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					that.addRelationshipId(result.body, callback);
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when reading a Relationship'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        that.addRelationshipId(result.body, callback);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when reading a Relationship'), null);
+                }
+            }
 		});
 };
 
@@ -346,17 +374,21 @@ Neo4j.prototype.updateRelationship = function(relationship_id, relationship_data
 		.put(that.url + '/db/data/relationship/' + relationship_id + '/properties')
 		.set(this.header)
 		.send(that.stringifyValueObjects(that.replaceNullWithString(relationship_data)))
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 204:
-					callback(null, true);
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when updating a Relationship.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 204:
+                        callback(null, true);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when updating a Relationship.'), null);
+                }
+            }
 		});
 };
 
@@ -372,17 +404,21 @@ Neo4j.prototype.insertIndex = function(index, callback) {
 			'name': index.index,
 			'config': index.config
 		})
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 201:
-					callback(null, result.body);
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when inserting an Index.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 201:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when inserting an Index.'), null);
+                }
+            }
 		});
 };
 
@@ -400,16 +436,18 @@ Neo4j.prototype.insertIndex = function(index, callback) {
 
 Neo4j.prototype.insertLabelIndex = function(label, property_key, callback) {
 	request
-			.post(this.url + '/db/data/schema/index/' + label)
-			.set(this.header)
-			.send({ 'property_keys' : [property_key] })
-			.end(function(result){
-				if(result.body) {
-					callback(null, result.body);
-				} else {
-					callback(new Error('Response is empty'), null);
-				}
-	});
+        .post(this.url + '/db/data/schema/index/' + label)
+        .set(this.header)
+        .send({ 'property_keys' : [property_key] })
+        .end(function(err, result){
+            if(err) {
+                callback(err);
+            } else if(result.body) {
+                callback(null, result.body);
+            } else {
+                callback(new Error('Response is empty'), null);
+            }
+        });
 };
 
 Neo4j.prototype.insertNodeIndex = function(index, callback) {
@@ -440,18 +478,22 @@ Neo4j.prototype.deleteIndex = function(index, callback) {
 	request
 		.del(this.url + '/db/data/index/' + index.type + '/' + index.index)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 204:
-					callback(null, true); // Index was deleted.
-					break;
-				case 404:
-					callback(null, false); // Index doesn't exist.
-					break;
-				default:
-					callback(new Error('Unknown Error while deleting Index'), null);
-			}
-	});
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 204:
+                        callback(null, true); // Index was deleted.
+                        break;
+                    case 404:
+                        callback(null, false); // Index doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('Unknown Error while deleting Index'), null);
+                }
+            }
+	    });
 };
 
 Neo4j.prototype.deleteNodeIndex = function(index, callback) {
@@ -464,39 +506,47 @@ Neo4j.prototype.deleteRelationshipIndex = function(index, callback) {
 
 Neo4j.prototype.deleteLabelIndex = function(label, property_key, callback) {
 	request
-	.del(this.url + '/db/data/schema/index/' + label + '/' + property_key)
-	.set(this.header)
-	.end(function(result) {
-		switch(result.statusCode) {
-			case 204:
-				callback(null, true); // Index was deleted.
-				break;
-			case 404:
-				callback(null, false); // Index doesn't exist.
-				break;
-			default:
-				callback(new Error('Unknown Error while deleting Index'), null);
-		}
-	});
+        .del(this.url + '/db/data/schema/index/' + label + '/' + property_key)
+        .set(this.header)
+        .end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 204:
+                        callback(null, true); // Index was deleted.
+                        break;
+                    case 404:
+                        callback(null, false); // Index doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('Unknown Error while deleting Index'), null);
+                }
+            }
+        });
 };
 
 function listIndexes (url, callback, header) {
 	request
-	.get(url)
-	.set(header)
-	.end(function(result) {
-		switch(result.statusCode) {
-			case 200:
-			case 204:
-				callback(null, result.body);
-				break;
-			case 404:
-				callback(null, false);
-				break;
-			default:
-				callback(new Error('HTTP Error ' + result.statusCode + ' when listing all indexes.'), null);
-		}
-	});
+        .get(url)
+        .set(header)
+        .end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                    case 204:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when listing all indexes.'), null);
+                }
+            }
+        });
 }
 
 Neo4j.prototype.listIndexes = function(indexType, callback) {
@@ -539,17 +589,21 @@ Neo4j.prototype.addItemToIndex = function (args, callback) {
 			'key': args.indexKey,
 			'value': args.indexValue
 		})
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					that.addNodeId(result.body, callback);
-					break;
-				case 201:
-					that.addNodeId(result.body, callback);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when adding an Item to an Index'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        that.addNodeId(result.body, callback);
+                        break;
+                    case 201:
+                        that.addNodeId(result.body, callback);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when adding an Item to an Index'), null);
+                }
+            }
 		});
 };
 
@@ -599,20 +653,24 @@ Neo4j.prototype.addLabelsToNode = function(nodeId, labels, callback) {
 			.post(url)
 		    .set(this.header)
 			.send(labels)
-			.end(function(result) {
-				switch(result.statusCode) {
-					case 204:
-						callback(null, true); // Labels added
-						break;
-					case 400:
-						callback(new Error(errorMsg), null); // Empty label
-						break;
-					case 404:
-						callback(null, false); // Node doesn't exist
-						break;
-					default:
-						callback(new Error('HTTP Error ' + result.statusCode + ' when adding a label to a node.'), null);
-				}
+			.end(function(err, result) {
+                if(err) {
+                    callback(err);
+                } else {
+                    switch(result.statusCode) {
+                        case 204:
+                            callback(null, true); // Labels added
+                            break;
+                        case 400:
+                            callback(new Error(errorMsg), null); // Empty label
+                            break;
+                        case 404:
+                            callback(null, false); // Node doesn't exist
+                            break;
+                        default:
+                            callback(new Error('HTTP Error ' + result.statusCode + ' when adding a label to a node.'), null);
+                    }
+                }
 			});
 	} else {
 		callback(new Error(errorMsg), null);
@@ -646,20 +704,24 @@ Neo4j.prototype.replaceLabelsFromNode = function(nodeId, labels, callback) {
 			.put(this.url + '/db/data/node/' + nodeId + '/labels')
 			.send(labels)
 		    .set(this.header)
-			.end(function(result) {
-				switch(result.statusCode) {
-					case 204:
-						callback(null, true);
-						break;
-					case 400:
-						callback(new Error(errorMsg), null); // Empty label
-						break;
-					case 404:
-						callback(null, false);
-						break;
-					default:
-						callback(new Error('HTTP Error ' + result.statusCode + ' when replacing labels.'), null);
-			}
+			.end(function(err, result) {
+                if(err) {
+                    callback(err);
+                } else {
+                    switch(result.statusCode) {
+                        case 204:
+                            callback(null, true);
+                            break;
+                        case 400:
+                            callback(new Error(errorMsg), null); // Empty label
+                            break;
+                        case 404:
+                            callback(null, false);
+                            break;
+                        default:
+                            callback(new Error('HTTP Error ' + result.statusCode + ' when replacing labels.'), null);
+		            }
+                }
 		});
 	} else {
 		callback(new Error(errorMsg), null);
@@ -687,18 +749,22 @@ Neo4j.prototype.deleteLabelFromNode = function(nodeId, label, callback) {
 	request
 		.del(this.url + '/db/data/node/' + nodeId + '/labels/'+ label)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 204:
-					callback(null, true); // Label was deleted.
-					break;
-				case 404:
-					callback(null, false); // Node doesn't exist.
-					break;
-				default:
-					callback(new Error('Unknown Error while deleting Index'), null);
-		}
-	});
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 204:
+                        callback(null, true); // Label was deleted.
+                        break;
+                    case 404:
+                        callback(null, false); // Node doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('Unknown Error while deleting Index'), null);
+                }
+            }
+	    });
 };
 
 /*	Get all nodes with a label
@@ -721,34 +787,38 @@ Neo4j.prototype.readNodesWithLabel = function(label, callback) {
 	request
 		.get(this.url + '/db/data/label/' + label + '/nodes')
 		.set(this.header)
-		.end(function(result) {
-			var body = result.body;
-			switch(result.statusCode) {
-				case 200:
-					if (body && body.length >= 1) {
-						step(
-							function addIds() {
-								var group = this.group();
-								body.forEach(function(node) {
-									that.addNodeId(node, group());
-								});
-							},
-							function sumUp(err, nodes) {
-								if (err) {
-									throw err;
-								}
-								callback(null, nodes);
-							});
-					} else {
-						callback(null, body);
-					}
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when reading a Relationship'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                var body = result.body;
+                switch(result.statusCode) {
+                    case 200:
+                        if (body && body.length >= 1) {
+                            step(
+                                function addIds() {
+                                    var group = this.group();
+                                    body.forEach(function(node) {
+                                        that.addNodeId(node, group());
+                                    });
+                                },
+                                function sumUp(err, nodes) {
+                                    if (err) {
+                                        throw err;
+                                    }
+                                    callback(null, nodes);
+                                });
+                        } else {
+                            callback(null, body);
+                        }
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when reading a Relationship'), null);
+                }
+            }
 		});
 };
 
@@ -776,34 +846,38 @@ Neo4j.prototype.readNodesWithLabelsAndProperties = function(labels, properties,
 		request
 			.get(this.url + '/db/data/label/' + labels + '/nodes?' + props)
 			.set(this.header)
-			.end(function(result) {
-				var body = result.body;
-				switch(result.statusCode) {
-					case 200:
-						if (body && body.length >= 1) {
-							step(
-								function addIds(){
-									var group = this.group();
-									body.forEach(function(node){
-										that.addNodeId(node, group());
-									});
-								},
-								function sumUp(err, nodes){
-									if(err) {
-										throw err;
-									}
-									callback(null, nodes);
-								});
-						} else {
-							callback(null, body);
-						}
-						break;
-					case 404:
-						callback(null, false);
-						break;
-					default:
-						callback(new Error('HTTP Error ' + result.statusCode + ' when reading Nodes.'), null);
-				}
+			.end(function(err, result) {
+                if(err) {
+                    callback(err);
+                } else {
+                    var body = result.body;
+                    switch(result.statusCode) {
+                        case 200:
+                            if (body && body.length >= 1) {
+                                step(
+                                    function addIds(){
+                                        var group = this.group();
+                                        body.forEach(function(node){
+                                            that.addNodeId(node, group());
+                                        });
+                                    },
+                                    function sumUp(err, nodes){
+                                        if(err) {
+                                            throw err;
+                                        }
+                                        callback(null, nodes);
+                                    });
+                            } else {
+                                callback(null, body);
+                            }
+                            break;
+                        case 404:
+                            callback(null, false);
+                            break;
+                        default:
+                            callback(new Error('HTTP Error ' + result.statusCode + ' when reading Nodes.'), null);
+                    }
+                }
 			});
 		} else { // Multiple labels or properties provided
 			var query = 'MATCH (data'+  cypher.labels(labels) + ') WHERE ' + cypher.where('data', properties) + ' RETURN data';
@@ -826,17 +900,21 @@ Neo4j.prototype.listAllLabels = function(callback) {
 	request
 	.get(this.url + '/db/data/labels')
 	.set(this.header)
-	.end(function(result) {
-		switch(result.statusCode) {
-			case 200:
-				callback(null, result.body);
-				break;
-			case 404:
-				callback(null, false);
-				break;
-			default:
-				callback(new Error('HTTP Error ' + result.statusCode + ' when listing all labels.'), null);
-		}
+	.end(function(err, result) {
+        if(err) {
+            callback(err);
+        } else {
+            switch(result.statusCode) {
+                case 200:
+                    callback(null, result.body);
+                    break;
+                case 404:
+                    callback(null, false);
+                    break;
+                default:
+                    callback(new Error('HTTP Error ' + result.statusCode + ' when listing all labels.'), null);
+            }
+        }
 	});
 };
 
@@ -864,17 +942,21 @@ var createUniquenessConstraint = function(label, property_key, callback) {
 		.post(that.url + '/db/data/schema/constraint/' + label + '/uniqueness')
 		.set(this.header)
 		.send({ 'property_keys' : [property_key] })
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, result.body);
-					break;
-				case 409:
-					callback(null, false); // Constraint already exists
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when creating a uniqueness contraint.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 409:
+                        callback(null, false); // Constraint already exists
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when creating a uniqueness contraint.'), null);
+                }
+            }
 		});
 };
 Neo4j.prototype.createUniquenessConstraint = createUniquenessConstraint;
@@ -900,17 +982,21 @@ Neo4j.prototype.readUniquenessConstraint = function(label, property, callback) {
 	request
 		.get(this.url + '/db/data/schema/constraint/' + label + '/uniqueness/' + property)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, result.body);
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when reading uniqueness constraints'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when reading uniqueness constraints'), null);
+                }
+            }
 	});
 };
 
@@ -937,17 +1023,21 @@ Neo4j.prototype.listAllUniquenessConstraintsForLabel = function(label, callback)
 	request
 		.get(this.url + '/db/data/schema/constraint/' + label + '/uniqueness')
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, result.body);
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when listing all uniqueness constraints.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when listing all uniqueness constraints.'), null);
+                }
+            }
 	});
 };
 
@@ -972,20 +1062,24 @@ Neo4j.prototype.listAllConstraintsForLabel = function(label, callback) {
 	}
 
 	request
-	.get(this.url + '/db/data/schema/constraint/' + label)
-	.set(this.header)
-	.end(function(result) {
-		switch(result.statusCode) {
-			case 200:
-				callback(null, result.body);
-				break;
-			case 404:
-				callback(null, false);
-				break;
-			default:
-				callback(new Error('HTTP Error ' + result.statusCode + ' when listing all constraints.'), null);
-		}
-	});
+        .get(this.url + '/db/data/schema/constraint/' + label)
+        .set(this.header)
+        .end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when listing all constraints.'), null);
+                }
+            }
+        });
 };
 
 
@@ -1004,20 +1098,24 @@ Neo4j.prototype.listAllConstraintsForLabel = function(label, callback) {
 
 Neo4j.prototype.listAllConstraints = function(callback) {
 	request
-	.get(this.url + '/db/data/schema/constraint')
-	.set(this.header)
-	.end(function(result) {
-		switch(result.statusCode) {
-			case 200:
-				callback(null, result.body);
-				break;
-			case 404:
-				callback(null, false);
-				break;
-			default:
-				callback(new Error('HTTP Error ' + result.statusCode + ' when listing all constraints.'), null);
-		}
-	});
+        .get(this.url + '/db/data/schema/constraint')
+        .set(this.header)
+        .end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when listing all constraints.'), null);
+                }
+            }
+        });
 };
 
 /*	Drop uniqueness constraint for a label and a property.
@@ -1038,17 +1136,21 @@ Neo4j.prototype.dropUniquenessContstraint = function(label, property_key, callba
 	request
 		.del(this.url + '/db/data/schema/constraint/' + label + '/uniqueness/' + property_key)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 204:
-					callback(null, true); // Constraint was deleted.
-					break;
-				case 404:
-					callback(null, false); // Constraint doesn't exist.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when removing a uniqueness contraint.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 204:
+                        callback(null, true); // Constraint was deleted.
+                        break;
+                    case 404:
+                        callback(null, false); // Constraint doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when removing a uniqueness contraint.'), null);
+                }
+            }
 		});
 };
 
@@ -1121,17 +1223,21 @@ Neo4j.prototype.beginTransaction = function(statements, callback) {
 		.post(this.url + '/db/data/transaction')
 		.set(this.header)
 		.send(statements)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 201:
-					that.addTransactionId(result.body, callback);
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when beginning transaction.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 201:
+                        that.addTransactionId(result.body, callback);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when beginning transaction.'), null);
+                }
+            }
 		});
 };
 
@@ -1176,23 +1282,27 @@ Neo4j.prototype.addStatementsToTransaction = function(transactionId, statements,
 		.post(this.url + '/db/data/transaction/' + transactionId)
 		.set(this.header)
 		.send(statements)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					that.addTransactionId(result.body, function afterAddingTransactionId (err, res) {
-						if (res.errors && res.errors.length > 0) {
-							callback(new Error('An error occured when adding statements to the transaction. See "errors" inside the result for more details.'), res);
-						} else {
-							callback(null, res);
-						}
-					});
-					break;
-				case 404:
-					callback(null, false); // Transaction doesn't exist.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when adding statements to transaction.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        that.addTransactionId(result.body, function afterAddingTransactionId (err, res) {
+                            if (res.errors && res.errors.length > 0) {
+                                callback(new Error('An error occured when adding statements to the transaction. See "errors" inside the result for more details.'), res);
+                            } else {
+                                callback(null, res);
+                            }
+                        });
+                        break;
+                    case 404:
+                        callback(null, false); // Transaction doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when adding statements to transaction.'), null);
+                }
+            }
 		});
 };
 
@@ -1227,17 +1337,21 @@ Neo4j.prototype.resetTimeoutTransaction = function(transactionId, callback) {
 		.post(this.url + '/db/data/transaction/' + transactionId)
 		.set(this.header)
 		.send({ statements : [ ]})
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					that.addTransactionId(result.body, callback);
-					break;
-				case 404:
-					callback(null, false); // Transaction doesn't exist.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when resetting transaction timeout.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        that.addTransactionId(result.body, callback);
+                        break;
+                    case 404:
+                        callback(null, false); // Transaction doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when resetting transaction timeout.'), null);
+                }
+            }
 		});
 };
 
@@ -1289,17 +1403,21 @@ Neo4j.prototype.commitTransaction = function(transactionId, statements, callback
 		.post(this.url + '/db/data/transaction/' + transactionId + '/commit')
 		.set(this.header)
 		.send(statements)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, result.body);
-					break;
-				case 404:
-					callback(null, false); // Transaction doesn't exist.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when commiting transaction.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false); // Transaction doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when commiting transaction.'), null);
+                }
+            }
 		});
 };
 
@@ -1327,17 +1445,21 @@ Neo4j.prototype.rollbackTransaction = function(transactionId, callback) {
 	request
 		.del(this.url + '/db/data/transaction/' + transactionId)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, true);
-					break;
-				case 404:
-					callback(null, false); // Transaction doesn't exist.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when rolling back transaction.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, true);
+                        break;
+                    case 404:
+                        callback(null, false); // Transaction doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when rolling back transaction.'), null);
+                }
+            }
 		});
 };
 
@@ -1405,17 +1527,21 @@ Neo4j.prototype.beginAndCommitTransaction = function(statements, callback) {
 		.set(this.header)
 		.set('X-Stream', true)
 		.send(statements)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, result.body);
-					break;
-				case 404:
-					callback(null, false); // Transaction doesn't exist.
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when beginning and commiting transaction.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, false); // Transaction doesn't exist.
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when beginning and commiting transaction.'), null);
+                }
+            }
 		});
 };
 
@@ -1429,14 +1555,18 @@ Neo4j.prototype.readRelationshipTypes = function(callback) {
 	request
 		.get(that.url + '/db/data/relationship/types')
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, result.body);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when retrieving relationship types.'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when retrieving relationship types.'), null);
+                }
+            }
 		});
 };
 
@@ -1466,17 +1596,21 @@ var readRelationshipsOfNode = function(node_id, options, callback) {
 	request
 		.get(url)
 		.set(this.header)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					that.addRelationshipIdForArray(result.body, callback);
-					break;
-				case 404:
-					callback(null, false);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when retrieving relationships for node ' + node_id), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        that.addRelationshipIdForArray(result.body, callback);
+                        break;
+                    case 404:
+                        callback(null, false);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when retrieving relationships for node ' + node_id), null);
+                }
+            }
 		});
 };
 // Create aliases
@@ -1517,58 +1651,62 @@ Neo4j.prototype.cypherQuery = function(query, params, include_stats, callback) {
 		.set(this.header)
 		.set('Content-Type', 'application/json')
 		.send(body)
-    .on('error', callback)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					if (result.body && result.body.data.length >= 1) {
-						var addIdsToColumnData = function(columnData, callback) {
-							step(
-								function addId() {
-									var group = this.group();
-									columnData.forEach(function(node) {
-										that.addNodeId(node, group());
-									});
-								},
-								function sumUp(err, nodes) {
-									if (err) {
-										throw err;
-									} else {
-										callback(null, nodes);
-									}
-								});
-						};
-
-						step(
-							function eachColumn() {
-								var group = this.group();
-								result.body.data.forEach(function(columnResult) {
-									addIdsToColumnData(columnResult, group());
-								});
-							},
-							function sumUp(err, columns) {
-								if (err) {
-									throw err;
-								} else {
-									// flatten the array if only one variable is getting returned to make it more convenient.
-									if (result.body.columns.length >= 2) {
-										result.body.data = columns;
-									} else {
-										result.body.data = [].concat.apply([], columns);
-									}
-									callback(null, result.body);
-								}
-							});
-					} else {
-						callback(null, result.body);
-					}
-					break;
-				case 404:
-					callback(null, null);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when running the cypher query against neo4j.\n' + result.body.exception + ': ' + result.body.message), null);
-			}
+        .on('error', callback)
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        if (result.body && result.body.data.length >= 1) {
+                            var addIdsToColumnData = function(columnData, callback) {
+                                step(
+                                    function addId() {
+                                        var group = this.group();
+                                        columnData.forEach(function(node) {
+                                            that.addNodeId(node, group());
+                                        });
+                                    },
+                                    function sumUp(err, nodes) {
+                                        if (err) {
+                                            throw err;
+                                        } else {
+                                            callback(null, nodes);
+                                        }
+                                    });
+                            };
+
+                            step(
+                                function eachColumn() {
+                                    var group = this.group();
+                                    result.body.data.forEach(function(columnResult) {
+                                        addIdsToColumnData(columnResult, group());
+                                    });
+                                },
+                                function sumUp(err, columns) {
+                                    if (err) {
+                                        throw err;
+                                    } else {
+                                        // flatten the array if only one variable is getting returned to make it more convenient.
+                                        if (result.body.columns.length >= 2) {
+                                            result.body.data = columns;
+                                        } else {
+                                            result.body.data = [].concat.apply([], columns);
+                                        }
+                                        callback(null, result.body);
+                                    }
+                                });
+                        } else {
+                            callback(null, result.body);
+                        }
+                        break;
+                    case 404:
+                        callback(null, null);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when running the cypher query against neo4j.\n' + result.body.exception + ': ' + result.body.message), null);
+                }
+            }
 		});
 };
 
@@ -1583,17 +1721,21 @@ Neo4j.prototype.batchQuery = function(query, callback) {
 		.set(this.header)
 		.set('Content-Type', 'application/json')
 		.send(query)
-		.end(function(result) {
-			switch(result.statusCode) {
-				case 200:
-					callback(null, result.body);
-					break;
-				case 404:
-					callback(null, null);
-					break;
-				default:
-					callback(new Error('HTTP Error ' + result.statusCode + ' when running the batch query against neo4j'), null);
-			}
+		.end(function(err, result) {
+            if(err) {
+                callback(err);
+            } else {
+                switch(result.statusCode) {
+                    case 200:
+                        callback(null, result.body);
+                        break;
+                    case 404:
+                        callback(null, null);
+                        break;
+                    default:
+                        callback(new Error('HTTP Error ' + result.statusCode + ' when running the batch query against neo4j'), null);
+                }
+            }
 		});
 };