So I have some module, in a work project that I'm portnig from GHC 6.12.3 to GHC 7.4.2, module Data.Monoid.Operator where import Data.Monoid (++) :: Monoid a => a -> a -> a (++) = mappend infixr 5 ++ This compiles happily on GHC 6.12.3, but on 7.4.2 says: src/Data/Monoid/Operator.hs:9:10: Ambiguous occurrence `++' It could refer to either `Data.Monoid.Operator.++', defined at src/Data/Monoid/Operator.hs:8:1 or `Prelude.++', imported from `Prelude' at src/Data/Monoid/Operator.hs:3:8-27 (and originally defined in `GHC.Base') It seems that it used to assign higher priority to the declared thing in the current module over the imported one. Is this intentional? I'd suspect not, given that if I comment the binding out: -- (++) :: Monoid a => a -> a -> a -- (++) = mappend I get: src/Data/Monoid/Operator.hs:9:10: The fixity signature for `++' lacks an accompanying binding (The fixity signature must be given where `++' is declared) Which seems to contradict the previous error message. Bug? Ciao! P.S. Yes, I know I can fix this by not importing Prelude. P.P.S Yes, I know there's a <> or <+> defined now, but I prefer (++), thanks.