diff --git a/internal/s3/client.go b/internal/s3/client.go
index 46b6ae5..d7c9031 100644
--- a/internal/s3/client.go
+++ b/internal/s3/client.go
@@ -90,9 +90,9 @@ func (c *Client) Multipart(bucket, key string, objPartSize int, payload goja.Arr
 		stats.Report(c.vu, objPutFails, 1)
 		return PutResponse{Success: false, Error: err.Error()}
 	}
-	sz := len(data)
+	size := len(payload.Bytes())
 	stats.Report(c.vu, objPutTotal, 1)
-	stats.ReportDataSent(c.vu, float64(sz))
+	stats.ReportDataSent(c.vu, float64(size))
 	stats.Report(c.vu, objPutDuration, metrics.D(time.Since(start)))
 	return PutResponse{Success: true}
 }