diff --git a/Foundation/NSCharacterSet.swift b/Foundation/NSCharacterSet.swift
index eb0dea800f..b7eb11e9f5 100644
--- a/Foundation/NSCharacterSet.swift
+++ b/Foundation/NSCharacterSet.swift
@@ -403,10 +403,6 @@ open class NSCharacterSet : NSObject, NSCopying, NSMutableCopying, NSSecureCodin
 }
 
 open class NSMutableCharacterSet : NSCharacterSet {
-
-    public convenience required init(coder aDecoder: NSCoder) {
-        NSUnimplemented()
-    }
     
     open func addCharacters(in aRange: NSRange) {
         CFCharacterSetAddCharactersInRange(_cfMutableObject , CFRangeMake(aRange.location, aRange.length))