diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index 059f37137f9a..919fd5bb14a8 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -388,7 +388,7 @@ static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
 	nchildren = nilfs_btree_node_get_nchildren(node);
 
 	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
-		     level > NILFS_BTREE_LEVEL_MAX ||
+		     level >= NILFS_BTREE_LEVEL_MAX ||
 		     nchildren < 0 ||
 		     nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) {
 		pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, flags = 0x%x, nchildren = %d\n",
diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index ff3fea3194c6..9abb763e4b86 100644
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -460,7 +460,7 @@ struct nilfs_btree_node {
 /* level */
 #define NILFS_BTREE_LEVEL_DATA          0
 #define NILFS_BTREE_LEVEL_NODE_MIN      (NILFS_BTREE_LEVEL_DATA + 1)
-#define NILFS_BTREE_LEVEL_MAX           14
+#define NILFS_BTREE_LEVEL_MAX           14	/* Max level (exclusive) */
 
 /**
  * struct nilfs_palloc_group_desc - block group descriptor