diff --git a/Data/FileStore/Types.hs b/Data/FileStore/Types.hs
index e950c7a..e116761 100644
--- a/Data/FileStore/Types.hs
+++ b/Data/FileStore/Types.hs
@@ -152,3 +152,3 @@ data FileStore = FileStore {
     -- | Save contents in the filestore.
-  , save           :: Contents a
+  , save           :: forall a . Contents a
                    => FilePath          -- Resource to save.
@@ -160,3 +160,3 @@ data FileStore = FileStore {
     -- | Retrieve the contents of the named resource.
-  , retrieve       :: Contents a
+  , retrieve       :: forall a . Contents a
                    => FilePath          -- Resource to retrieve.