diff -r a7a0115061ec -r dbc2426a600d src/HOL/Library/code_test.ML
--- a/src/HOL/Library/code_test.ML	Fri Mar 22 11:23:17 2019 +0100
+++ b/src/HOL/Library/code_test.ML	Fri Mar 22 18:04:52 2019 +0100
@@ -467,9 +467,9 @@
 
     val compiled_path = Path.append path (Path.basic "test")
     val compile_cmd =
-      "\"$ISABELLE_OCAMLFIND\" ocamlopt -w pu -package zarith -linkpkg " ^
+      "\"$ISABELLE_OCAMLFIND\" ocamlopt -w pu -package zarith -linkpkg" ^
       " -o " ^ File.bash_path compiled_path ^ " -I " ^ File.bash_path path ^ " " ^
-      File.bash_path code_path ^ " " ^ File.bash_path driver_path
+      File.bash_path code_path ^ " " ^ File.bash_path driver_path ^ " </dev/null"
 
     val run_cmd = File.bash_path compiled_path
   in