diff --git a/System/Cmd.hs b/System/Cmd.hs
index 5fba064614785ec67afa35404d301813a889bdeb..a00e22892718d499121ef7862dd3a1cba86c166c 100644
--- a/System/Cmd.hs
+++ b/System/Cmd.hs
@@ -1,3 +1,7 @@
+{-# LANGUAGE CPP #-}
+#if __GLASGOW_HASKELL__ >= 701
+{-# LANGUAGE Trustworthy #-}
+#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  System.Cmd
diff --git a/System/Process.hs b/System/Process.hs
index 45401d4990375f20b655205544570fb535c5c473..bba4f520bc781ae97af0df6acc3687fd925f8fd4 100644
--- a/System/Process.hs
+++ b/System/Process.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE CPP, ForeignFunctionInterface #-}
 #if __GLASGOW_HASKELL__ >= 701
+{-# LANGUAGE Trustworthy #-}
 -- not available prior to 7.1
 {-# LANGUAGE InterruptibleFFI #-}
 #endif
diff --git a/System/Process/Internals.hs b/System/Process/Internals.hs
index b68f268a812bd3ab5f8c591a64adc559334fa0d1..36aec6b46c311f96029be76b4230d065339cf334 100644
--- a/System/Process/Internals.hs
+++ b/System/Process/Internals.hs
@@ -1,4 +1,8 @@
-{-# LANGUAGE CPP, ForeignFunctionInterface, RecordWildCards #-}
+{-# LANGUAGE CPP #-}
+#if __GLASGOW_HASKELL__ >= 701
+{-# LANGUAGE Trustworthy #-}
+#endif
+{-# LANGUAGE ForeignFunctionInterface, RecordWildCards #-}
 {-# OPTIONS_HADDOCK hide #-}
 {-# OPTIONS_GHC -w #-}
 -- XXX We get some warnings on Windows