diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index 9132c5cb41f1..06a66327333d 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -25,10 +25,11 @@
 
 #include <linux/types.h>
 
+#define PB_migratetype_bits 3
 /* Bit indices that affect a whole block of pages */
 enum pageblock_bits {
 	PB_migrate,
-	PB_migrate_end = PB_migrate + 3 - 1,
+	PB_migrate_end = PB_migrate + PB_migratetype_bits - 1,
 			/* 3 bits required for migrate types */
 	PB_migrate_skip,/* If set the block is skipped by compaction */
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b4fcf211ca69..cd1c9d32ef9a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -431,6 +431,7 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
 	unsigned long old_word, word;
 
 	BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
+	BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));
 
 	bitmap = get_pageblock_bitmap(page, pfn);
 	bitidx = pfn_to_bitidx(page, pfn);