diff --git a/Sources/WebLinking.swift b/Sources/WebLinking.swift
index bfe533d..cce0ae4 100644
--- a/Sources/WebLinking.swift
+++ b/Sources/WebLinking.swift
@@ -193,7 +193,7 @@ func takeFirst(_ input: [String]) -> (String, ArraySlice<String>) {
 func trim(_ lhs: Character, _ rhs: Character) -> (String) -> String {
   return { input in
     if input.hasPrefix("\(lhs)") && input.hasSuffix("\(rhs)") {
-      return String(input[input.characters.index(after: input.startIndex)..<input.characters.index(before: input.endIndex)])
+      return String(input[input.index(after: input.startIndex)..<input.index(before: input.endIndex)])
     }
 
     return input
diff --git a/WebLinking.xcodeproj/project.pbxproj b/WebLinking.xcodeproj/project.pbxproj
index c593c22..1ec799f 100644
--- a/WebLinking.xcodeproj/project.pbxproj
+++ b/WebLinking.xcodeproj/project.pbxproj
@@ -181,16 +181,16 @@
 			attributes = {
 				LastSwiftMigration = 0700;
 				LastSwiftUpdateCheck = 0700;
-				LastUpgradeCheck = 0900;
+				LastUpgradeCheck = 0920;
 				ORGANIZATIONNAME = Cocode;
 				TargetAttributes = {
 					272A93981A6E67F8004B3785 = {
 						CreatedOnToolsVersion = 6.2;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0920;
 					};
 					272A93A31A6E67F8004B3785 = {
 						CreatedOnToolsVersion = 6.2;
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0920;
 					};
 				};
 			};
@@ -383,6 +383,8 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SKIP_INSTALL = YES;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
+				SWIFT_SWIFT3_OBJC_INFERENCE = On;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -402,6 +404,8 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "org.cocode.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SKIP_INSTALL = YES;
+				SWIFT_SWIFT3_OBJC_INFERENCE = On;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
@@ -417,6 +421,8 @@
 				INFOPLIST_FILE = Tests/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.cocode.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_SWIFT3_OBJC_INFERENCE = On;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -428,6 +434,8 @@
 				INFOPLIST_FILE = Tests/Info.plist;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.cocode.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_SWIFT3_OBJC_INFERENCE = On;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
diff --git a/WebLinking.xcodeproj/xcshareddata/xcschemes/WebLinking.xcscheme b/WebLinking.xcodeproj/xcshareddata/xcschemes/WebLinking.xcscheme
index 0a1e713..434dcdd 100644
--- a/WebLinking.xcodeproj/xcshareddata/xcschemes/WebLinking.xcscheme
+++ b/WebLinking.xcodeproj/xcshareddata/xcschemes/WebLinking.xcscheme
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0900"
+   LastUpgradeVersion = "0920"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"