diff --git a/ConstMath/Pass.hs b/ConstMath/Pass.hs
index 96537db..e7c155c 100644
--- a/ConstMath/Pass.hs
+++ b/ConstMath/Pass.hs
@@ -2,6 +2,7 @@
 {-# LANGUAGE PatternGuards #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE TupleSections #-}
+{-# LANGUAGE ImpredicativeTypes #-}
 
 {-# OPTIONS_GHC -Wall #-}
 module ConstMath.Pass (
@@ -146,7 +147,8 @@ mkUnaryCollapseNum fnE opts expr@(App f1 (App f2 (Lit lit)))
             | otherwise = do
                 let sub = fnE (from d)
                 msgResult
-                return (App f2 (mkLit sub))
+                dflags <- getDynFlags
+                return (App f2 (mkLit dflags sub))
 mkUnaryCollapseNum _ _ expr = return expr
 
 mkBinaryCollapse :: (forall a. RealFloat a => (a -> a -> a))
diff --git a/tests/Make.hs b/tests/Make.hs
index b46ef2b..789849b 100644
--- a/tests/Make.hs
+++ b/tests/Make.hs
@@ -1,7 +1,7 @@
 module Main where
 
-import System.Cmd
 import System.Directory
+import System.Process
 
 import Paths_const_math_ghc_plugin