diff --git a/AFNetworking/AFURLRequestSerialization.m b/AFNetworking/AFURLRequestSerialization.m
index 5e231cf..8679d97 100755
--- a/AFNetworking/AFURLRequestSerialization.m
+++ b/AFNetworking/AFURLRequestSerialization.m
@@ -205,7 +205,7 @@ NSArray * AFQueryStringPairsFromKeyAndValue(NSString *key, id value) {
     if (userAgent) {
         if (![userAgent canBeConvertedToEncoding:NSASCIIStringEncoding]) {
             NSMutableString *mutableUserAgent = [userAgent mutableCopy];
-            CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, CFSTR("Any-Latin; Latin-ASCII; [:^ASCII:] Remove"), false);
+            CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, (__bridge CFStringRef)@"Any-Latin; Latin-ASCII; [:^ASCII:] Remove", false);
             userAgent = mutableUserAgent;
         }
         [self setValue:userAgent forHTTPHeaderField:@"User-Agent"];