diff --git a/src/BeSimple/SoapCommon/Mime/Part.php b/src/BeSimple/SoapCommon/Mime/Part.php
index 476c00d..04c6bb5 100644
--- a/src/BeSimple/SoapCommon/Mime/Part.php
+++ b/src/BeSimple/SoapCommon/Mime/Part.php
@@ -163,6 +163,6 @@ class Part extends PartHeader
      */
     protected function generateContentId()
     {
-        return 'urn:uuid:' . Helper::generateUUID();
+        return 'part-' . Helper::generateUUID() . '@response.info';
     }
 }
\ No newline at end of file