diff -r 170daa8170be -r 6a9a8ef5e4c6 src/Tools/Code/code_ml.ML
--- a/src/Tools/Code/code_ml.ML	Fri Jan 25 22:13:47 2019 +0000
+++ b/src/Tools/Code/code_ml.ML	Fri Jan 25 22:13:48 2019 +0000
@@ -887,7 +887,7 @@
     (target_OCaml, {serializer = serializer_ocaml, literals = literals_ocaml,
       check = {env_var = "ISABELLE_OCAML",
         make_destination = fn p => Path.append p (Path.explode "ROOT.ocaml"),
-        make_command = fn _ => "\"$ISABELLE_OCAML\" -w pu nums.cma ROOT.ocaml"},
+        make_command = fn _ => "\"$ISABELLE_OCAML\" -w pu -safe-string nums.cma ROOT.ocaml"},
       evaluation_args = []})
   #> Code_Target.set_printings (Type_Constructor ("fun",
     [(target_SML, SOME (2, fun_syntax)), (target_OCaml, SOME (2, fun_syntax))]))