diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5e1d4e3..3a37ba7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1838,7 +1838,7 @@
 int btrfs_cow_block(struct btrfs_trans_handle *trans,
 		    struct btrfs_root *root, struct extent_buffer *buf,
 		    struct extent_buffer *parent, int parent_slot,
-		    struct extent_buffer **cow_ret, u64 prealloc_dest);
+		    struct extent_buffer **cow_ret);
 int btrfs_copy_root(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *root,
 		      struct extent_buffer *buf,