NSTimer keeps a strong reference of a ViewController, but in Xcode Memory graph debugger it shows it as a weak reference ( i.e by a non-darker line ). is this expected or a bug? Context : I was fixing a memory leak issue, where the Timer inside the View controller was Not invalidated properly ( In turn Not allowing my view controller to get deallocated, even after being dismissed ). So, when I invalidated the timer, View controller also got properly deallocated. which means Timer was indeed keeping a strong reference! Then why is it showing as a weak reference in the Xcode Debug Memory graph?