diff -r bb18957ad21e -r df6caf649ff7 src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp
--- a/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Fri Jul 10 16:01:20 2009 -0700
+++ b/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Tue Jul 14 15:40:39 2009 -0700
@@ -293,10 +293,6 @@
   if (G1SteadyStateUsed < 50) {
     vm_exit_during_initialization("G1SteadyStateUsed must be at least 50%.");
   }
-  if (UseConcMarkSweepGC) {
-    vm_exit_during_initialization("-XX:+UseG1GC is incompatible with "
-                                  "-XX:+UseConcMarkSweepGC.");
-  }
 
   initialize_gc_policy_counters();