--- old/src/share/vm/gc/g1/g1ConcurrentMark.cpp	2017-08-22 15:36:27.833167712 +0200
+++ new/src/share/vm/gc/g1/g1ConcurrentMark.cpp	2017-08-22 15:36:27.697167716 +0200
@@ -200,7 +200,7 @@
     return NULL;
   }
 
-  size_t cur_idx = Atomic::add(1, &_hwm) - 1;
+  size_t cur_idx = Atomic::add(1u, &_hwm) - 1;
   if (cur_idx >= _chunk_capacity) {
     return NULL;
   }