diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 947a7e96f91d..ea4b9dcf43b7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1474,7 +1474,7 @@ static bool __zone_watermark_ok(struct zone *z, int order, unsigned long mark,
 	long min = mark;
 	int o;
 
-	free_pages -= (1 << order) + 1;
+	free_pages -= (1 << order) - 1;
 	if (alloc_flags & ALLOC_HIGH)
 		min -= min / 2;
 	if (alloc_flags & ALLOC_HARDER)