diff --git a/yesod-core/Yesod/Core/Handler.hs b/yesod-core/Yesod/Core/Handler.hs
index 4b580cc9..9e6c1333 100644
--- a/yesod-core/Yesod/Core/Handler.hs
+++ b/yesod-core/Yesod/Core/Handler.hs
@@ -10,6 +10,7 @@
 {-# LANGUAGE TypeFamilies               #-}
 {-# LANGUAGE RankNTypes                 #-}
 {-# LANGUAGE DeriveDataTypeable         #-}
+{-# LANGUAGE ScopedTypeVariables        #-}
 ---------------------------------------------------------
 --
 -- Module        : Yesod.Handler