[Haskell-cafe] confusion with fgl and ghc6

I don't know whether this is a bug in fgl, in ghc, or I'm just confused. Any ideas? This is on debian/sid. GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude> import Data.Graph.Inductive.Example Prelude Data.Graph.Inductive.Example> star 6 <interactive>:1:0: Ambiguous type variable `gr' in the constraint: `Data.Graph.Inductive.Graph.Graph gr' arising from a use of `star' at <interactive>:1:0-5 Probable fix: add a type signature that fixes these type variable(s) Prelude Data.Graph.Inductive.Example>