StateT space leak

Consider the following program: module A where import Control.Monad.State f :: StateT Int IO () f = (sequence_ $ repeat $ return ()) t = runStateT f 0 When t is evaluated under ghci or hugs, the program quickly runs out of heap memory. What's going on here? Is this inherent in StateT monad? If so, then this is very surprising, I would expect f to run in constant space for any sensible monad. Wojtek