diff --git a/mm/internal.h b/mm/internal.h
index d1ddd71..3ac544f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -103,12 +103,13 @@
 	struct zonelist *zonelist;
 	nodemask_t *nodemask;
 	struct zoneref *preferred_zoneref;
-	int classzone_idx;
 	int migratetype;
 	enum zone_type high_zoneidx;
 	bool spread_dirty_pages;
 };
 
+#define ac_classzone_idx(ac) zonelist_zone_idx(ac->preferred_zoneref)
+
 /*
  * Locate the struct page for both the matching buddy in our
  * pair (buddy1) and the combined O(n+1) page they form (page).