For iOS5 compatibility you should do something like:
```Objective-C
#if OS_OBJECT_USE_OBJC
@property (nonatomic, strong) dispatch_queue_t queue;
#else
@property (nonatomic, assign) dispatch_queue_t queue;
#endif
```
and release it...
```Objective-C
#if !(OS_OBJECT_USE_OBJC)
if (self.queue) {
    dispatch_release(self.queue);
}
#endif
```