dispatch_semaphore_wait does not wait on semaphore

I have developed the following method, which checks the app's ability to communicate with the server. The method performs a simple query and knows that if it gets a result, the app should be connected (basic ping mechanism). - (BOOL)isAppConnected { __block BOOL isConnected = NO; dispatch_semaphore_t semaphore = dispatch_semaphore_create(0); [[SFRestAPI sharedInstance] performSOQLQuery:@"SELECT id FROM Account LIMIT 1" failBlock:^(NSError *e) { isConnected = NO; NSLog(@"NOT CONNECTED %@", e); NSLog(@"fail block ON THE MAIN THREAD? %hhd", [NSThread isMainThread]); dispatch_semaphore_signal(semaphore); } completeBlock:^(NSDictionary *dict) { isConnected = YES; NSLog(@"%@", dict); NSLog(@"complete block ON THE MAIN THREAD? %hhd", [NSThread isMainThread]); dispatch_semaphore_signal(semaphore); }]; // if the wait times-out we will receive a non-zero result and can assume no connection to SF //When using: DISPATCH_TIME_FOREVER the app hangs forever!! int waitResult = dispatch_semaphore_wait(semaphore, 30 * NSEC_PER_SEC); NSLog(@"waitResult: %d", waitResult); return isConnected; } I am using the 'dispatch_semaphore_wait' as suggested in the Apple documentation My goal is to wait on the response or a short timeout to figure out if we really have a valid connection. With the code above, 'dispatch_semaphore_wait' never actually waits, i.e. execution does not stop at that line but it continues immediately (always returning 49 as the result to the dispatch_semaphore_wait call). That is unless I use DISPATCH_TIME_FOREVER in which case the app hangs forever... At the moment I am calling this method from the main thread. I am aware that this is a bad idea, but I wanted to see this working as expected before refactoring. What could be causing this behaviour? Thanks.