diff --git a/SDWebImage/SDWebImageDownloader.m b/SDWebImage/SDWebImageDownloader.m
index 1c008d0c..c6aa6269 100644
--- a/SDWebImage/SDWebImageDownloader.m
+++ b/SDWebImage/SDWebImageDownloader.m
@@ -135,7 +135,10 @@ static NSString *const kCompletedCallbackKey = @"completed";
                                                          progress:^(NSInteger receivedSize, NSInteger expectedSize) {
                                                              SDWebImageDownloader *sself = wself;
                                                              if (!sself) return;
-                                                             NSArray *callbacksForURL = [sself callbacksForURL:url];
+                                                             __block NSArray *callbacksForURL;
+                                                             dispatch_sync(sself.barrierQueue, ^{
+                                                                 callbacksForURL = sself.URLCallbacks[url];
+                                                             });
                                                              for (NSDictionary *callbacks in callbacksForURL) {
                                                                  SDWebImageDownloaderProgressBlock callback = callbacks[kProgressCallbackKey];
                                                                  if (callback) callback(receivedSize, expectedSize);
@@ -144,10 +147,13 @@ static NSString *const kCompletedCallbackKey = @"completed";
                                                         completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished) {
                                                             SDWebImageDownloader *sself = wself;
                                                             if (!sself) return;
-                                                            NSArray *callbacksForURL = [sself callbacksForURL:url];
-                                                            if (finished) {
-                                                                [sself removeCallbacksForURL:url];
-                                                            }
+                                                            __block NSArray *callbacksForURL;
+                                                            dispatch_barrier_sync(sself.barrierQueue, ^{
+                                                                callbacksForURL = sself.URLCallbacks[url];
+                                                                if (finished) {
+                                                                    [sself.URLCallbacks removeObjectForKey:url];
+                                                                }
+                                                            });
                                                             for (NSDictionary *callbacks in callbacksForURL) {
                                                                 SDWebImageDownloaderCompletedBlock callback = callbacks[kCompletedCallbackKey];
                                                                 if (callback) callback(image, data, error, finished);
@@ -156,7 +162,9 @@ static NSString *const kCompletedCallbackKey = @"completed";
                                                         cancelled:^{
                                                             SDWebImageDownloader *sself = wself;
                                                             if (!sself) return;
-                                                            [sself removeCallbacksForURL:url];
+                                                            dispatch_barrier_async(sself.barrierQueue, ^{
+                                                                [sself.URLCallbacks removeObjectForKey:url];
+                                                            });
                                                         }];
         
         if (wself.username && wself.password) {
@@ -210,20 +218,6 @@ static NSString *const kCompletedCallbackKey = @"completed";
     });
 }
 
-- (NSArray *)callbacksForURL:(NSURL *)url {
-    __block NSArray *callbacksForURL;
-    dispatch_sync(self.barrierQueue, ^{
-        callbacksForURL = self.URLCallbacks[url];
-    });
-    return [callbacksForURL copy];
-}
-
-- (void)removeCallbacksForURL:(NSURL *)url {
-    dispatch_barrier_async(self.barrierQueue, ^{
-        [self.URLCallbacks removeObjectForKey:url];
-    });
-}
-
 - (void)setSuspended:(BOOL)suspended {
     [self.downloadQueue setSuspended:suspended];
 }
diff --git a/Tests/Podfile b/Tests/Podfile
index 7ac80ded..7f86b807 100644
--- a/Tests/Podfile
+++ b/Tests/Podfile
@@ -4,7 +4,7 @@ xcodeproj 'SDWebImage Tests'
 workspace '../SDWebImage'
 
 def import_pods
-  pod 'Expecta'                       # A Matcher Framework for Objective-C/Cocoa
+  pod 'Expecta', '<=0.3.1'                    # A Matcher Framework for Objective-C/Cocoa
   pod 'SDWebImage', :path => '../'
 end