diff --git a/AFNetworking/AFHTTPRequestOperation.h b/AFNetworking/AFHTTPRequestOperation.h
index ea6bfd0..122099e 100644
--- a/AFNetworking/AFHTTPRequestOperation.h
+++ b/AFNetworking/AFHTTPRequestOperation.h
@@ -74,12 +74,12 @@
 @property (readonly) BOOL hasAcceptableContentType;
 
 /** 
- The callback dispatch queue on success. If this is NULL (default), the main queue is used.
+ The callback dispatch queue on success. If `NULL` (default), the main queue is used.
  */
 @property (nonatomic) dispatch_queue_t successCallbackQueue;
 
 /** 
- The callback dispatch queue on failure. If this is NULL (default), the main queue is used.
+ The callback dispatch queue on failure. If `NULL` (default), the main queue is used.
  */
 @property (nonatomic) dispatch_queue_t failureCallbackQueue;
 
@@ -107,18 +107,3 @@
                               failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error))failure;
 
 @end
-
-
-@interface AFHTTPRequestOperation (AFInternal)
-
-/**
- Executes the successBlock on the corresponding successCallbackQueue.
- */
-- (void)dispatchSuccessBlock:(void (^)(AFHTTPRequestOperation *operation, id responseObject))successBlock responseObject:(id)responseObject;
-
-/**
- Executes the failureBlock on the corresponding failureCallbackQueue.
- */
-- (void)dispatchFailureBlock:(void (^)(AFHTTPRequestOperation *operation, NSError *error))failureBlock;
-
-@end
\ No newline at end of file
diff --git a/AFNetworking/AFHTTPRequestOperation.m b/AFNetworking/AFHTTPRequestOperation.m
index 591c56e..b20c406 100644
--- a/AFNetworking/AFHTTPRequestOperation.m
+++ b/AFNetworking/AFHTTPRequestOperation.m
@@ -49,8 +49,17 @@
     [_acceptableStatusCodes release];
     [_acceptableContentTypes release];
     [_HTTPError release];
-    if (_successCallbackQueue) { dispatch_release(_successCallbackQueue), _successCallbackQueue=NULL;}
-    if (_failureCallbackQueue) { dispatch_release(_failureCallbackQueue), _failureCallbackQueue=NULL;}
+    
+    if (_successCallbackQueue) { 
+        dispatch_release(_successCallbackQueue);
+        _successCallbackQueue = NULL;
+    }
+    
+    if (_failureCallbackQueue) { 
+        dispatch_release(_failureCallbackQueue); 
+        _failureCallbackQueue = NULL;
+    }
+    
     [super dealloc];
 }
 
@@ -92,7 +101,6 @@
 
 - (void)setSuccessCallbackQueue:(dispatch_queue_t)successCallbackQueue {
     if (successCallbackQueue != _successCallbackQueue) {
-        
         if (_successCallbackQueue) {
             dispatch_release(_successCallbackQueue);
         }
@@ -106,7 +114,6 @@
 
 - (void)setFailureCallbackQueue:(dispatch_queue_t)failureCallbackQueue {
     if (failureCallbackQueue != _failureCallbackQueue) {
-        
         if (_failureCallbackQueue) {
             dispatch_release(_failureCallbackQueue);
         }
@@ -127,9 +134,17 @@
         }
         
         if (self.error) {
-            [self dispatchFailureBlock:failure];
+            if (failure) {
+                dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
+                    failure(self, self.error);
+                });
+            }
         } else {
-            [self dispatchSuccessBlock:success responseObject:self.responseString];
+            if (success) {
+                dispatch_async(self.successCallbackQueue ? self.successCallbackQueue : dispatch_get_main_queue(), ^{
+                    success(self, self.responseString);
+                });
+            }
         }
     };
 }
@@ -140,22 +155,4 @@
     return YES;
 }
 
-#pragma mark - AFInternal
-
-- (void)dispatchSuccessBlock:(void (^)(AFHTTPRequestOperation *operation, id responseObject))successBlock responseObject:(id)responseObject {
-    if (successBlock) {
-        dispatch_async(self.successCallbackQueue ? self.successCallbackQueue : dispatch_get_main_queue(), ^{
-            successBlock(self, responseObject);
-        });
-    }
-}
-
-- (void)dispatchFailureBlock:(void (^)(AFHTTPRequestOperation *operation, NSError *error))failureBlock {
-    if (failureBlock) {
-        dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
-            failureBlock(self, self.error);
-        });
-    }
-}
-
 @end
diff --git a/AFNetworking/AFImageRequestOperation.m b/AFNetworking/AFImageRequestOperation.m
index f732a3c..de8237e 100644
--- a/AFNetworking/AFImageRequestOperation.m
+++ b/AFNetworking/AFImageRequestOperation.m
@@ -109,11 +109,11 @@ static dispatch_queue_t image_request_operation_processing_queue() {
     [requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
         if (success) {
             NSImage *image = responseObject;
-            
+
             if (imageProcessingBlock) {
                 image = imageProcessingBlock(image);
             }
-                        
+            
             success(operation.request, operation.response, image);
         }
     } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
@@ -230,9 +230,17 @@ static dispatch_queue_t image_request_operation_processing_queue() {
         
         dispatch_async(image_request_operation_processing_queue(), ^(void) {
             if (self.error) {
-                [self dispatchFailureBlock:failure];
+                if (failure) {
+                    dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
+                        failure(self, self.error);
+                    });
+                }
             } else {            
-                [self dispatchSuccessBlock:success responseObject:self.responseImage];
+                if (success) {
+                    dispatch_async(self.successCallbackQueue ? self.successCallbackQueue : dispatch_get_main_queue(), ^{
+                        success(self, self.responseImage);
+                    });
+                }
             }
         });        
     };  
diff --git a/AFNetworking/AFJSONRequestOperation.m b/AFNetworking/AFJSONRequestOperation.m
index 6d39413..9046dd0 100644
--- a/AFNetworking/AFJSONRequestOperation.m
+++ b/AFNetworking/AFJSONRequestOperation.m
@@ -124,15 +124,27 @@ static dispatch_queue_t json_request_operation_processing_queue() {
         }
         
         if (self.error) {
-            [self dispatchFailureBlock:failure];
+            if (failure) {
+                dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
+                    failure(self, self.error);
+                });
+            }
         } else {
             dispatch_async(json_request_operation_processing_queue(), ^(void) {
                 id JSON = self.responseJSON;
                 
                 if (self.JSONError) {
-                    [self dispatchFailureBlock:failure];
+                    if (failure) {
+                        dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
+                            failure(self, self.error);
+                        });
+                    }
                 } else {
-                    [self dispatchSuccessBlock:success responseObject:JSON];
+                    if (success) {
+                        dispatch_async(self.successCallbackQueue ? self.successCallbackQueue : dispatch_get_main_queue(), ^{
+                            success(self, JSON);
+                        });
+                    }                    
                 }
             });
         }
diff --git a/AFNetworking/AFPropertyListRequestOperation.m b/AFNetworking/AFPropertyListRequestOperation.m
index d294cd2..ea9d216 100644
--- a/AFNetworking/AFPropertyListRequestOperation.m
+++ b/AFNetworking/AFPropertyListRequestOperation.m
@@ -124,15 +124,27 @@ static dispatch_queue_t property_list_request_operation_processing_queue() {
         }
         
         if (self.error) {
-            [self dispatchFailureBlock:failure];
+            if (failure) {
+                dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
+                    failure(self, self.error);
+                });
+            }
         } else {
             dispatch_async(property_list_request_operation_processing_queue(), ^(void) {
                 id propertyList = self.responsePropertyList;
                 
                 if (self.propertyListError) {
-                    [self dispatchFailureBlock:failure];
-                }else {
-                    [self dispatchSuccessBlock:success responseObject:propertyList];
+                    if (failure) {
+                        dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
+                            failure(self, self.error);
+                        });
+                    }
+                } else {
+                    if (success) {
+                        dispatch_async(self.successCallbackQueue ? self.successCallbackQueue : dispatch_get_main_queue(), ^{
+                            success(self, propertyList);
+                        });
+                    } 
                 }
             });
         }
diff --git a/AFNetworking/AFXMLRequestOperation.m b/AFNetworking/AFXMLRequestOperation.m
index 7b50fd6..79c5272 100644
--- a/AFNetworking/AFXMLRequestOperation.m
+++ b/AFNetworking/AFXMLRequestOperation.m
@@ -24,7 +24,6 @@
 
 #include <Availability.h>
 
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
 static dispatch_queue_t af_xml_request_operation_processing_queue;
 static dispatch_queue_t xml_request_operation_processing_queue() {
     if (af_xml_request_operation_processing_queue == NULL) {
@@ -33,14 +32,13 @@ static dispatch_queue_t xml_request_operation_processing_queue() {
     
     return af_xml_request_operation_processing_queue;
 }
-#endif
 
 @interface AFXMLRequestOperation ()
 @property (readwrite, nonatomic, retain) NSXMLParser *responseXMLParser;
 #if __MAC_OS_X_VERSION_MIN_REQUIRED
 @property (readwrite, nonatomic, retain) NSXMLDocument *responseXMLDocument;
 #endif
-@property (readwrite, nonatomic, retain) NSError *error;
+@property (readwrite, nonatomic, retain) NSError *XMLError;
 
 + (NSSet *)defaultAcceptableContentTypes;
 + (NSSet *)defaultAcceptablePathExtensions;
@@ -51,7 +49,7 @@ static dispatch_queue_t xml_request_operation_processing_queue() {
 #if __MAC_OS_X_VERSION_MIN_REQUIRED
 @synthesize responseXMLDocument = _responseXMLDocument;
 #endif
-@synthesize error = _XMLError;
+@synthesize XMLError = _XMLError;
 
 + (AFXMLRequestOperation *)XMLParserRequestOperationWithRequest:(NSURLRequest *)urlRequest
                                                         success:(void (^)(NSURLRequest *request, NSHTTPURLResponse *response, NSXMLParser *XMLParser))success
@@ -76,34 +74,20 @@ static dispatch_queue_t xml_request_operation_processing_queue() {
                                                           success:(void (^)(NSURLRequest *request, NSHTTPURLResponse *response, NSXMLDocument *document))success
                                                           failure:(void (^)(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, NSXMLDocument *document))failure
 {
-    AFXMLRequestOperation *operation = [[[self alloc] initWithRequest:urlRequest] autorelease];
-    operation.completionBlock = ^ {
-        if ([operation isCancelled]) {
-            return;
+    AFXMLRequestOperation *requestOperation = [[[self alloc] initWithRequest:urlRequest] autorelease];
+    [requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, __unused id responseObject) {
+        if (success) {
+            NSXMLDocument *XMLDocument = [(AFXMLRequestOperation *)operation responseXMLDocument];            
+            success(operation.request, operation.response, XMLDocument);
         }
-        
-        if (operation.error) {
-            if (failure) {
-                NSXMLDocument *XMLDocument = operation.responseXMLDocument;
-                
-                dispatch_async(dispatch_get_main_queue(), ^(void) {
-                    failure(operation.request, operation.response, operation.error, XMLDocument);
-                });
-            }
-        } else {
-            dispatch_async(xml_request_operation_processing_queue(), ^(void) {
-                if (success) {
-                    NSXMLDocument *XMLDocument = operation.responseXMLDocument;
-
-                    dispatch_async(dispatch_get_main_queue(), ^(void) {
-                        success(operation.request, operation.response, XMLDocument);
-                    });
-                }
-            });
+    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
+        if (failure) {
+            NSXMLDocument *XMLDocument = [(AFXMLRequestOperation *)operation responseXMLDocument];
+            failure(operation.request, operation.response, error, XMLDocument);
         }
-    };
+    }];
     
-    return operation;
+    return requestOperation;
 }
 #endif
 
@@ -151,7 +135,7 @@ static dispatch_queue_t xml_request_operation_processing_queue() {
     if (!_responseXMLDocument && [self.responseData length] > 0 && [self isFinished]) {
         NSError *error = nil;
         self.responseXMLDocument = [[[NSXMLDocument alloc] initWithData:self.responseData options:0 error:&error] autorelease];
-        self.error = error;
+        self.XMLError = error;
     }
     
     return _responseXMLDocument;
@@ -186,11 +170,23 @@ static dispatch_queue_t xml_request_operation_processing_queue() {
             return;
         }
         
-        if (self.error) {
-            [self dispatchFailureBlock:failure];
-        } else {
-            [self dispatchSuccessBlock:success responseObject:self.responseXMLParser];
-        }
+        dispatch_async(xml_request_operation_processing_queue(), ^(void) {
+            NSXMLParser *XMLParser = self.responseXMLParser;
+            
+            if (self.error) {
+                if (failure) {
+                    dispatch_async(self.failureCallbackQueue ? self.failureCallbackQueue : dispatch_get_main_queue(), ^{
+                        failure(self, self.error);
+                    });
+                }
+            } else {
+                if (success) {
+                    dispatch_async(self.successCallbackQueue ? self.successCallbackQueue : dispatch_get_main_queue(), ^{
+                        success(self, XMLParser);
+                    });
+                } 
+            }
+        });
     };    
 }