--- old/src/cpu/arm/vm/vm_version_arm_64.cpp	2017-06-08 00:14:32.846893510 -0700
+++ new/src/cpu/arm/vm/vm_version_arm_64.cpp	2017-06-08 00:14:32.726882662 -0700
@@ -201,7 +201,9 @@
     }
   }
 
-  AllocatePrefetchDistance = 128;
+  if (FLAG_IS_DEFAULT(AllocatePrefetchDistance)) {
+    AllocatePrefetchDistance = 128;
+  }
 
 #ifdef COMPILER2
   FLAG_SET_DEFAULT(UseFPUForSpilling, true);