--- old/src/share/vm/runtime/arguments.cpp	2012-12-21 12:59:46.000000000 +0100
+++ new/src/share/vm/runtime/arguments.cpp	2012-12-21 12:59:45.000000000 +0100
@@ -1083,10 +1083,6 @@
   }
 }
 
-// If the user has chosen ParallelGCThreads > 0, we set UseParNewGC
-// if it's not explictly set or unset. If the user has chosen
-// UseParNewGC and not explicitly set ParallelGCThreads we
-// set it, unless this is a single cpu machine.
 void Arguments::set_parnew_gc_flags() {
   assert(!UseSerialGC && !UseParallelOldGC && !UseParallelGC && !UseG1GC,
          "control point invariant");
@@ -1095,14 +1091,14 @@
   // Turn off AdaptiveSizePolicy for parnew until it is complete.
   disable_adaptive_size_policy("UseParNewGC");
 
-  if (ParallelGCThreads == 0) {
-    FLAG_SET_DEFAULT(ParallelGCThreads,
-                     Abstract_VM_Version::parallel_worker_threads());
-    if (ParallelGCThreads == 1) {
-      FLAG_SET_DEFAULT(UseParNewGC, false);
-      FLAG_SET_DEFAULT(ParallelGCThreads, 0);
+  if (FLAG_IS_DEFAULT(ParallelGCThreads)) {
+    assert(ParallelGCThreads == 0, "Default value for ParallelGCThreads should be 0");
+    uint par_gc_threads = Abstract_VM_Version::parallel_worker_threads();
+    if (par_gc_threads > 1) {
+      FLAG_SET_DEFAULT(ParallelGCThreads, par_gc_threads);
     }
   }
+
   if (UseParNewGC) {
     // By default YoungPLABSize and OldPLABSize are set to 4096 and 1024 respectively,
     // these settings are default for Parallel Scavenger. For ParNew+Tenured configuration