diff -r fca40adc6342 -r 047129a6e200 src/Pure/ML/ml_compiler0.ML
--- a/src/Pure/ML/ml_compiler0.ML	Wed Apr 06 19:03:29 2016 +0200
+++ b/src/Pure/ML/ml_compiler0.ML	Wed Apr 06 19:50:27 2016 +0200
@@ -147,11 +147,13 @@
 
 (* export type-dependent functions *)
 
-ML_Compiler0.use_text
-  (ML_Compiler0.make_context
-    (ML_Name_Space.global_values
-      [("prettyRepresentation", "ML_system_pretty"),
-       ("addPrettyPrinter", "ML_system_pp"),
-       ("addOverload", "ML_system_overload")]))
-  {debug = false, file = "", line = 0, verbose = false}
-  "open PolyML RunCall" handle ERROR _ => ();
+if Thread_Data.is_virtual then ()
+else
+  ML_Compiler0.use_text
+    (ML_Compiler0.make_context
+      (ML_Name_Space.global_values
+        [("prettyRepresentation", "ML_system_pretty"),
+         ("addPrettyPrinter", "ML_system_pp"),
+         ("addOverload", "ML_system_overload")]))
+    {debug = false, file = "", line = 0, verbose = false}
+    "open PolyML RunCall";