diff --git a/index.js b/index.js
index fa009d1..64b9d63 100644
--- a/index.js
+++ b/index.js
@@ -32,7 +32,10 @@ UndoManager.prototype = {
     {
         if (!this.canUndo)
             return;
-    
+
+        while (this._groupingLevel)
+            this.endGroup();
+
         this._index--;
 
         this._isUndoing = true;
diff --git a/test.html b/test.html
index 844672f..0c90950 100644
--- a/test.html
+++ b/test.html
@@ -148,6 +148,23 @@
             console.log("Redo once");
             manager.redo();
             test("obj.foo === 20", obj.foo === 20);
+
+            console.log("Increment obj.foo 4 times within two unclosed nested groups");
+            manager.beginGroup();
+            increment(2);
+            manager.beginGroup();
+            increment(2);
+            test("obj.foo === 24", obj.foo === 24);
+
+            console.log("Undo twice");
+            manager.undo();
+            manager.undo();
+            test("obj.foo === 2", obj.foo === 2);
+            
+            console.log("Redo twice");
+            manager.redo();
+            manager.redo();
+            test("obj.foo === 24", obj.foo === 24);
         });
 
     </script>