1 files changed, 3 insertions, 2 deletions
diff --git a/haddock-api/src/Haddock/Interface/Specialize.hs b/haddock-api/src/Haddock/Interface/Specialize.hs
index f0cf08a1..0cac818d 100644
--- a/haddock-api/src/Haddock/Interface/Specialize.hs
+++ b/haddock-api/src/Haddock/Interface/Specialize.hs
@@ -203,11 +203,12 @@ setInternalOccName occ name =
 
 
 -- | Compute set of free variables of given type.
-freeVariables :: HsType GhcRn -> Set Name
+freeVariables :: forall p. (NamedThing (IdP p), DataId p, Typeable p)
+              => HsType p -> Set Name
 freeVariables =
     everythingWithState Set.empty Set.union query
   where
-    query term ctx = case cast term :: Maybe (HsType GhcRn) of
+    query term ctx = case cast term :: Maybe (HsType p) of
         Just (HsForAllTy _ bndrs _) ->
             (Set.empty, Set.union ctx (bndrsNames bndrs))
         Just (HsTyVar _ _ (L _ name))