diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e90d7c597ef3a651a15458b8b3108a02065c6d3e..28491a82e6456fdf3b1ba1c350bcd74240f06976 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -978,6 +978,7 @@ static noinline int cow_file_range(struct inode *inode,
 
 	num_bytes = ALIGN(end - start + 1, blocksize);
 	num_bytes = max(blocksize,  num_bytes);
+	ASSERT(num_bytes <= btrfs_super_total_bytes(fs_info->super_copy));
 
 	inode_should_defrag(BTRFS_I(inode), start, end, num_bytes, SZ_64K);
 
@@ -1008,8 +1009,6 @@ static noinline int cow_file_range(struct inode *inode,
 		}
 	}
 
-	BUG_ON(num_bytes > btrfs_super_total_bytes(fs_info->super_copy));
-
 	alloc_hint = get_extent_allocation_hint(inode, start, num_bytes);
 	btrfs_drop_extent_cache(BTRFS_I(inode), start,
 			start + num_bytes - 1, 0);