diff --git a/convert/main.c b/convert/main.c
index c9e50c03..77b7c051 100644
--- a/convert/main.c
+++ b/convert/main.c
@@ -984,7 +984,8 @@ static int make_convert_data_block_groups(struct btrfs_trans_handle *trans,
 			u64 cur_backup = cur;
 
 			len = min(max_chunk_size,
-				  cache->start + cache->size - cur);
+				  round_up(cache->start + cache->size,
+					   BTRFS_STRIPE_LEN) - cur);
 			ret = btrfs_alloc_data_chunk(trans, fs_info, &cur_backup, len);
 			if (ret < 0)
 				break;