diff -r 8956e19bdffb -r 73d61cd3f8e9 src/share/vm/runtime/arguments.cpp
--- a/src/share/vm/runtime/arguments.cpp	Tue Oct 07 14:35:40 2014 -0700
+++ b/src/share/vm/runtime/arguments.cpp	Wed Oct 08 14:13:23 2014 -0700
@@ -1646,6 +1646,12 @@
                      Abstract_VM_Version::parallel_worker_threads());
   }
 
+#if INCLUDE_ALL_GCS
+  if (G1ConcRefinementThreads == 0) {
+    FLAG_SET_DEFAULT(G1ConcRefinementThreads, ParallelGCThreads);
+  }
+#endif
+
   // MarkStackSize will be set (if it hasn't been set by the user)
   // when concurrent marking is initialized.
   // Its value will be based upon the number of parallel marking threads.