Objective C - Weak reference to super class?

I am trying to call a method on super class inside a block. In order to avoid a retain-cycle I need a weak reference to super. How would I get a weak reference to super?

[self somethingWithCompletion:^(){
   [super doStuff];
}];

I tried the following but gives a compile error.

__weak MySuperClass *superReference = super;