interview question: C

An engineer at a customer's site asked me an interview question:

// Returns x/y, or 0 if y is 0. Never crashes.
int buggy_div(int x, int y)
{
  if (y == 0)
    return 0;
  return x/y;
}

Why the function above would crash on my computer? There are indeed parameters that make it crash.
Normally I am lagging on this type of problems when you need a quick answer, but it took me 2 minutes to solve this one.
Ideas? Comments are screened for one day.