diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index cd9a12ca281d..b3f13105659d 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -1368,7 +1368,7 @@ __acquires(bitmap->lock)
 	if (bitmap->bp[page].hijacked ||
 	    bitmap->bp[page].map == NULL)
 		csize = ((sector_t)1) << (bitmap->chunkshift +
-					  PAGE_COUNTER_SHIFT - 1);
+					  PAGE_COUNTER_SHIFT);
 	else
 		csize = ((sector_t)1) << bitmap->chunkshift;
 	*blocks = csize - (offset & (csize - 1));