diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 926b1d34e55c..f75333d7b78a 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -4283,7 +4283,7 @@ static int btrfs_log_prealloc_extents(struct btrfs_trans_handle *trans,
 	struct extent_buffer *leaf;
 	int slot;
 	int ins_nr = 0;
-	int start_slot;
+	int start_slot = 0;
 	int ret;
 
 	if (!(inode->flags & BTRFS_INODE_PREALLOC))