Std lib equivalent for liftM concat . sequence

A couple of days ago I had need for:

> concatM :: Monad m => [m [a]] -> m [a]
> concatM = liftM concat . sequence

but found no such thing in the std libs, except perhaps for msum (I
don't want to add instances for MonadPlus. Should I have to?). Have I
missed something trivial?

Alistair