src/Pure/Concurrent/synchronized.ML

--- a/src/Pure/Concurrent/synchronized.ML	Thu Mar 17 16:56:44 2016 +0100
+++ b/src/Pure/Concurrent/synchronized.ML	Fri Mar 18 16:26:35 2016 +0100
@@ -66,4 +66,9 @@
 
 end;
 
+
+(* toplevel pretty printing *)
+
+val _ = PolyML.addPrettyPrinter (fn depth => fn pretty => fn var => pretty (value var, depth));
+
 end;