diff --git a/Language/Haskell/GhcMod/GHCApi.hs b/Language/Haskell/GhcMod/GHCApi.hs
index e7b460f..7bad3fd 100644
--- a/Language/Haskell/GhcMod/GHCApi.hs
+++ b/Language/Haskell/GhcMod/GHCApi.hs
@@ -20,7 +20,6 @@ import Language.Haskell.GhcMod.GhcPkg
 import Control.Applicative ((<$>))
 import Control.Monad (forM, void)
 import CoreMonad (liftIO)
-import Data.IntSet (IntSet, empty)
 import Data.Maybe (isJust, fromJust)
 import Exception (ghandle, SomeException(..))
 import GHC (Ghc, GhcMonad, DynFlags(..), GhcLink(..), HscTarget(..), LoadHowMuch(..))
@@ -188,12 +187,12 @@ withDynFlags setFlag body = G.gbracket setup teardown (\_ -> body)
 ----------------------------------------------------------------
 
 setNoWaringFlags :: DynFlags -> DynFlags
-setNoWaringFlags df = df { warningFlags = empty}
+setNoWaringFlags df = df { warningFlags = Gap.emptyWarnFlags}
 
 setAllWaringFlags :: DynFlags -> DynFlags
 setAllWaringFlags df = df { warningFlags = allWarningFlags }
 
-allWarningFlags :: IntSet
+allWarningFlags :: Gap.WarnFlags
 allWarningFlags = unsafePerformIO $ do
     mlibdir <- getSystemLibDir
     G.runGhc mlibdir $ do
diff --git a/Language/Haskell/GhcMod/Gap.hs b/Language/Haskell/GhcMod/Gap.hs
index d8b1b19..1ceb355 100644
--- a/Language/Haskell/GhcMod/Gap.hs
+++ b/Language/Haskell/GhcMod/Gap.hs
@@ -28,6 +28,8 @@ module Language.Haskell.GhcMod.Gap (
   , GapThing(..)
   , fromTyThing
   , fileModSummary
+  , WarnFlags
+  , emptyWarnFlags
   ) where
 
 import Control.Applicative hiding (empty)
@@ -71,6 +73,10 @@ import Control.Arrow hiding ((<+>))
 import Data.Convertible
 #endif
 
+#if __GLASGOW_HASKELL__ >= 704
+import qualified Data.IntSet as I (IntSet, empty)
+#endif
+
 ----------------------------------------------------------------
 ----------------------------------------------------------------
 --
@@ -359,3 +365,16 @@ fromTyThing (ADataCon d)               = GtA $ dataConRepType d
 #endif
 fromTyThing (ATyCon t)                 = GtT t
 fromTyThing _                          = GtN
+
+----------------------------------------------------------------
+----------------------------------------------------------------
+
+#if __GLASGOW_HASKELL__ >= 704
+type WarnFlags = I.IntSet
+emptyWarnFlags :: WarnFlags
+emptyWarnFlags = I.empty
+#else
+type WarnFlags = [WarningFlag]
+emptyWarnFlags :: WarnFlags
+emptyWarnFlags = []
+#endif