--- old/src/share/vm/gc_implementation/g1/g1InCSetState.hpp	2014-12-16 11:05:45.137851429 +0100
+++ new/src/share/vm/gc_implementation/g1/g1InCSetState.hpp	2014-12-16 11:05:45.079849745 +0100
@@ -30,6 +30,7 @@
 
 // Per-region state during garbage collection.
 struct InCSetState {
+ private:
   // We use different types to represent the state value. Particularly SPARC puts
   // values in structs from "left to right", i.e. MSB to LSB. This results in many
   // unnecessary shift operations when loading and storing values of this type.
@@ -75,7 +76,7 @@
 
 #ifdef ASSERT
   bool is_default() const              { return is_not_in_cset(); }
-  bool is_valid() const                { return _value < Num; }
+  bool is_valid() const                { return (_value >= Humongous) && (_value < Num); }
   bool is_valid_gen() const            { return (_value >= Young && _value <= Old); }
 #endif
 };