diff -r 33439faadd67 -r 975c9ba50a41 src/HOL/Tools/Quickcheck/narrowing_generators.ML
--- a/src/HOL/Tools/Quickcheck/narrowing_generators.ML	Fri Aug 19 19:01:00 2011 -0700
+++ b/src/HOL/Tools/Quickcheck/narrowing_generators.ML	Thu Aug 18 13:37:41 2011 +0200
@@ -251,7 +251,7 @@
           (if contains_existentials then pnf_narrowing_engine else narrowing_engine)
         val _ = File.write main_file main
         val executable = File.shell_path (Path.append in_path (Path.basic "isabelle_quickcheck_narrowing"))
-        val cmd = "exec \"$ISABELLE_GHC\" -fglasgow-exts " ^
+        val cmd = "exec \"$ISABELLE_GHC\" -XRankNTypes -XScopedTypeVariables " ^
           (space_implode " " (map File.shell_path [code_file, narrowing_engine_file, main_file])) ^
           " -o " ^ executable ^ ";"
         val (result, compilation_time) =