diff --git a/internal/s3/client.go b/internal/s3/client.go
index 346d325..46b6ae5 100644
--- a/internal/s3/client.go
+++ b/internal/s3/client.go
@@ -77,13 +77,14 @@ func (c *Client) Multipart(bucket, key string, objPartSize int, payload goja.Arr
 		return PutResponse{Success: false, Error: fmt.Sprintf("part size '%d' must be greater than '%d'(5 MB)", objPartSize, multipartUploadMinPartSize)}
 	}
 	start := time.Now()
-	uploader := manager.NewUploader(c.cli)
+	uploader := manager.NewUploader(c.cli, func(u *manager.Uploader) {
+	    u.PartSize = objPartSize
+	    uploader.Concurrency = concurrency
+    })
 	result, err := uploader.Upload(context.TODO(), &s3.PutObjectInput{
 	    Bucket: aws.String(bucket),
 	    Key:    aws.String(key),
 	    Body:   payload.Bytes(),
-	    PartSize: objPartSize,
-	    Concurrency: concurrency,
     })
     if err != nil {
 		stats.Report(c.vu, objPutFails, 1)