--- old/src/cpu/x86/vm/vm_version_x86.hpp	2017-06-08 08:26:38.867772305 -0700
+++ new/src/cpu/x86/vm/vm_version_x86.hpp	2017-06-08 08:26:38.741760906 -0700
@@ -820,10 +820,18 @@
     }
     return count;
   }
+
   static intx allocate_prefetch_style() {
     assert(AllocatePrefetchStyle >= 0, "AllocatePrefetchStyle should be positive");
     // Return 0 if AllocatePrefetchDistance was not defined.
-    return AllocatePrefetchDistance > 0 ? AllocatePrefetchStyle : 0;
+    if (AllocatePrefetchDistance > 0) {
+      return AllocatePrefetchStyle;
+    } else {
+      if (!FLAG_IS_DEFAULT(AllocatePrefetchStyle) && (AllocatePrefetchStyle != 0)) {
+        warning("AllocatePrefetchDistance is not set. Ignoring AllocatePrefetchStyle flag.");
+      }
+      return 0;
+    }
   }
 
   // Prefetch interval for gc copy/scan == 9 dcache lines.  Derived from