--- old/src/share/vm/opto/loopTransform.cpp	2015-10-08 22:15:51.009224202 +0200
+++ new/src/share/vm/opto/loopTransform.cpp	2015-10-08 22:15:50.957225444 +0200
@@ -927,6 +927,7 @@
   // Check for 'n' being pinned in the backedge.
   if( n->in(0) && n->in(0) == back_ctrl ) {
     assert(clones.find(n->_idx) == NULL, "dead loop");
+    assert(n->Opcode() != Op_ShenandoahWriteBarrier, "no wbs yet");
     x = n->clone();             // Clone a copy of 'n' to preheader
     clones.push(x, n->_idx);
     x->set_req( 0, preheader_ctrl ); // Fix x's control input to preheader