OI in 7.10.1

Please, what is wrong here? --------------------------------------------------------------- module OI where class Foo a where foo :: a -> Bool instance Foo Bool where foo _ = True data C a = C a instance {-# OVERLAPPING #-} Foo a => Foo (C a) where foo (C a) = foo a instance {-# OVERLAPPING #-} Foo (C Bool) where foo _ = False --------------------------------------------------------------- By this I intended to test the overlapping instance control. I set the pragma as it is shown in the User guide. And ghc-7.10.1 -c -XFlexibleInstances OI.hs reports "Unrecognised pragma". Please, advise, ------ Sergei