diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 208f3eea3641fa4645c085f50716d6cd477a17cc..d98cfd3b64ff002b5b5704f33daf7aeeea9aec14 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -944,7 +944,7 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
 out:
 	for (i = last_map; i < num; i++) {
 		/* Don't zap current batch's valid persistent grants. */
-		if(i >= last_map + segs_to_map)
+		if(i >= map_until)
 			pages[i]->persistent_gnt = NULL;
 		pages[i]->handle = BLKBACK_INVALID_HANDLE;
 	}