--- old/src/share/vm/opto/parse1.cpp	2014-12-19 14:44:46.938240381 +0100
+++ new/src/share/vm/opto/parse1.cpp	2014-12-19 14:44:46.765926684 +0100
@@ -986,7 +986,16 @@
   if (tf()->range()->cnt() > TypeFunc::Parms) {
     const Type* ret_type = tf()->range()->field_at(TypeFunc::Parms);
     Node*       ret_phi  = _gvn.transform( _exits.argument(0) );
-    assert(_exits.control()->is_top() || !_gvn.type(ret_phi)->empty(), "return value must be well defined");
+#ifdef ASSERT 
+    {
+      // In case of concurrent class loading, the type we set for the
+      // ret_phi in build_exits() may have been too optimistic and the
+      // ret_phi may be top now.
+      MutexLockerEx ml(Compile_lock, Mutex::_no_safepoint_check_flag);
+      assert(_exits.control()->is_top() || !_gvn.type(ret_phi)->empty() ||
+             (ret_type->isa_ptr() && C->env()->system_dictionary_modification_counter_changed()), "return value must be well defined");
+    }
+#endif
     _exits.push_node(ret_type->basic_type(), ret_phi);
   }