diff -r bc15dcaed517 -r 5dbbd33c3236 src/Pure/type.ML
--- a/src/Pure/type.ML	Thu Oct 04 20:29:13 2007 +0200
+++ b/src/Pure/type.ML	Thu Oct 04 20:29:24 2007 +0200
@@ -396,7 +396,7 @@
 fun unify (tsig as TSig {classes = (_, classes), ...}) TU (tyenv, maxidx) =
   let
     val tyvar_count = ref maxidx;
-    fun gen_tyvar S = TVar (("'a", inc tyvar_count), S);
+    fun gen_tyvar S = TVar ((Name.aT, inc tyvar_count), S);
 
     fun mg_domain a S = Sorts.mg_domain classes a S
       handle Sorts.CLASS_ERROR _ => raise TUNIFY;