diff --git a/src/Panic.hs b/src/Panic.hs
index bc506f9dd..863feddb9 100644
--- a/src/Panic.hs
+++ b/src/Panic.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+
 module Panic (
   FatalError(..),
   panic,