diff --git a/AFNetworking/AFJSONUtilities.h b/AFNetworking/AFJSONUtilities.h
index 2fb59a8..bc70e07 100644
--- a/AFNetworking/AFJSONUtilities.h
+++ b/AFNetworking/AFJSONUtilities.h
@@ -43,16 +43,15 @@ static NSData * AFJSONEncode(id object, NSError **error) {
         
         [invocation invoke];
         [invocation getReturnValue:&data];
-    } else if (_SBJSONSelector && [object respondsToSelector:_SBJSONSelector]) {
-        NSString *JSONString = nil;
-        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[object methodSignatureForSelector:_SBJSONSelector]];
-        invocation.target = object;
+    } else if (_SBJSONSelector && [NSString instancesRespondToSelector:_SBJSONSelector]) {
+        // Create a string representation of JSON, to use SBJSON -`JSONValue` category method
+        NSString *string = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];
+        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[string methodSignatureForSelector:_SBJSONSelector]];
+        invocation.target = string;
         invocation.selector = _SBJSONSelector;
         
         [invocation invoke];
-        [invocation getReturnValue:&data];
-        
-        data = [JSONString dataUsingEncoding:NSUTF8StringEncoding];
+        [invocation getReturnValue:&JSON];
     } else if (_YAJLSelector && [object respondsToSelector:_YAJLSelector]) {
         @try {
             NSString *JSONString = nil;