diff --git a/AFNetworking/AFHTTPClient.m b/AFNetworking/AFHTTPClient.m
index 3af22a2..f9d2166 100644
--- a/AFNetworking/AFHTTPClient.m
+++ b/AFNetworking/AFHTTPClient.m
@@ -81,7 +81,7 @@ static NSString * AFBase64EncodedStringFromString(NSString *string) {
 }
 
 static NSString * AFPercentEscapedQueryStringPairMemberFromStringWithEncoding(NSString *string, NSStringEncoding encoding) {
-    static NSString * const kAFCharactersToBeEscaped = @":/?&=;+!@#$()~'";
+    static NSString * const kAFCharactersToBeEscaped = @":/?&=;+!@#$()~',";
     static NSString * const kAFCharactersToLeaveUnescaped = @"[].";
 
 	return (__bridge_transfer  NSString *)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (__bridge CFStringRef)string, (__bridge CFStringRef)kAFCharactersToLeaveUnescaped, (__bridge CFStringRef)kAFCharactersToBeEscaped, CFStringConvertNSStringEncodingToEncoding(encoding));