Tweak error message

diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index 0272c54..fc41c8a 100644 (file)
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -656,7 +656,7 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving overlap_flag tvs cls cl
        mb_std_err = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon
        std_err = derivingThingErr cls cls_tys tc_app $
                  vcat [fromJust mb_std_err,
-                       ptext SLIT("Try -fglasgow-exts for GHC's newtype-deriving extension")]
+                       ptext SLIT("Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension")]
 
        -- Here is the plan for newtype derivings.  We see
        --        newtype T a1...an = MkT (t ak+1...an) deriving (.., C s1 .. sm, ...)