diff --git a/src/compiler/GF/Compile/PGFtoHaskell.hs b/src/compiler/GF/Compile/PGFtoHaskell.hs
index 89366568d..fc17e4e4e 100644
--- a/src/compiler/GF/Compile/PGFtoHaskell.hs
+++ b/src/compiler/GF/Compile/PGFtoHaskell.hs
@@ -39,7 +39,7 @@ grammar2haskell opts name gr = foldr (++++) [] $
           lexical cat = haskellOption opts HaskellLexical && isLexicalCat opts cat
           gId | haskellOption opts HaskellNoPrefix = id
               | otherwise = ("G"++)
-          pragmas | gadt = ["{-# OPTIONS_GHC -fglasgow-exts #-}"]
+          pragmas | gadt = ["{-# OPTIONS_GHC -fglasgow-exts #-}","{-# LANGUAGE GADTs #-}"]
                   | otherwise = []
           types | gadt = datatypesGADT gId lexical gr'
                 | otherwise = datatypes gId lexical gr'