diff --git a/Source/String.swift b/Source/String.swift
index cbc79ee..0e30e8c 100644
--- a/Source/String.swift
+++ b/Source/String.swift
@@ -26,6 +26,6 @@ import Foundation
 
 extension String {
   func urlEncode() -> String? {
-    return self.stringByAddingPercentEncodingWithAllowedCharacters(NSCharacterSet.allowedURLCharacterSet)
+    return stringByAddingPercentEncodingWithAllowedCharacters(.allowedURLCharacterSet)
   }
 }