diff --git a/AFNetworking/AFURLConnectionOperation.m b/AFNetworking/AFURLConnectionOperation.m
index 8015bd6..be7e10f 100644
--- a/AFNetworking/AFURLConnectionOperation.m
+++ b/AFNetworking/AFURLConnectionOperation.m
@@ -149,8 +149,10 @@ static inline NSString * AFKeyPathFromOperationState(AFOperationState state) {
     
     __block id _blockSelf = self;
     [super setCompletionBlock:^ {
-        block();
-        [_blockSelf setCompletionBlock:nil];
+        dispatch_async(dispatch_get_main_queue(), ^(void) {
+            block();
+            [_blockSelf setCompletionBlock:nil];
+        });
     }];
 }