diff -r 1f4b011c5738 -r adeac19dd410 src/Tools/Code/code_ml.ML
--- a/src/Tools/Code/code_ml.ML	Tue Apr 19 13:05:50 2016 +0200
+++ b/src/Tools/Code/code_ml.ML	Mon Apr 18 20:56:11 2016 +0200
@@ -868,7 +868,7 @@
 val _ = Theory.setup
   (Code_Target.add_language
     (target_SML, { serializer = serializer_sml, literals = literals_sml,
-      check = { env_var = "ISABELLE_TOOL",
+      check = { env_var = "",
         make_destination = fn p => Path.append p (Path.explode "ROOT.ML"),
         make_command = fn _ =>
           "isabelle process -e 'datatype ref = datatype Unsynchronized.ref' -f 'ROOT.ML' -l Pure" } })