--- a/src/share/vm/runtime/arguments.cpp	Thu Feb 24 13:41:58 2011 +0100
+++ b/src/share/vm/runtime/arguments.cpp	Thu Mar 03 19:25:53 2011 +0100
@@ -1416,7 +1416,7 @@
   // by ergonomics.
   if (MaxHeapSize <= max_heap_for_compressed_oops()) {
 #if !defined(COMPILER1) || defined(TIERED)
-    if (FLAG_IS_DEFAULT(UseCompressedOops) && !UseG1GC) {
+    if (FLAG_IS_DEFAULT(UseCompressedOops)) {
       FLAG_SET_ERGO(bool, UseCompressedOops, true);
     }
 #endif
@@ -3145,6 +3145,19 @@
   // Set flags if Aggressive optimization flags (-XX:+AggressiveOpts) enabled.
   set_aggressive_opts_flags();
 
+  // Turn off biased locking for locking debug mode flags,
+  // which are subtlely different from each other but neither works with
+  // biased locking.
+  if (!UseFastLocking || UseHeavyMonitors) {
+    if (!FLAG_IS_DEFAULT(UseBiasedLocking) && UseBiasedLocking) {
+      // flag set to true on command line; warn the user that they
+      // can't enable biased locking here
+      warning("Biased Locking is not supported with locking debug flags"
+              "; ignoring UseBiasedLocking flag." );
+    }
+    UseBiasedLocking = false;
+  }
+
 #ifdef CC_INTERP
   // Clear flags not supported by the C++ interpreter
   FLAG_SET_DEFAULT(ProfileInterpreter, false);