diff --git a/[refs] b/[refs]
index 666dbe7f96e8..d8471cf3c03d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 29d0b218c87ace1078e08bb32c2e72fc96fa3db3
+refs/heads/master: 217fd5e709f029c125a9d39de5f13387407f131a
diff --git a/trunk/drivers/block/xen-blkback/blkback.c b/trunk/drivers/block/xen-blkback/blkback.c
index 477a17c20820..2cf8381a1c6e 100644
--- a/trunk/drivers/block/xen-blkback/blkback.c
+++ b/trunk/drivers/block/xen-blkback/blkback.c
@@ -164,7 +164,7 @@ static void make_response(struct xen_blkif *blkif, u64 id,
 
 #define foreach_grant_safe(pos, n, rbtree, node) \
 	for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
-	     (n) = rb_next(&(pos)->node); \
+	     (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
 	     &(pos)->node != NULL; \
 	     (pos) = container_of(n, typeof(*(pos)), node), \
 	     (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)