diff --git a/backend/s3/s3.go b/backend/s3/s3.go
index 09e32d1c1..9a1419eeb 100644
--- a/backend/s3/s3.go
+++ b/backend/s3/s3.go
@@ -5944,8 +5944,8 @@ func (f *Fs) OpenChunkWriter(ctx context.Context, remote string, src fs.ObjectIn
 		chunkSize:            int64(chunkSize),
 		size:                 size,
 		f:                    f,
-		bucket:               mOut.Bucket,
-		key:                  mOut.Key,
+		bucket:               ui.req.Bucket,
+		key:                  ui.req.Key,
 		uploadID:             mOut.UploadId,
 		multiPartUploadInput: &mReq,
 		completedParts:       make([]types.CompletedPart, 0),