Asynchronously dispatched recursive blocks

Suppose I run this code:

__block int step = 0;

__block dispatch_block_t myBlock;

myBlock = ^{
     if(step == STEPS_COUNT)
     {
         return;
     }

     step++;
     dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC / 2);
     dispatch_after(delay, dispatch_get_current_queue(), myBlock);
};

dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC / 2);
dispatch_after(delay, dispatch_get_current_queue(), myBlock);

The block is invoked once from outside. When the inner invocation is reached, the program crashes without any details. If I use direct invocations everywhere instead of GCD dispatches, everything works fine.

I've also tried calling dispatch_after with a copy of the block. I don't know if this was a step in the right direction or not, but it wasn't enough to make it work.

Ideas?