diff --git a/src/SAML2/HTTPPost.php b/src/SAML2/HTTPPost.php
index ca7552a8a..219de0ffc 100644
--- a/src/SAML2/HTTPPost.php
+++ b/src/SAML2/HTTPPost.php
@@ -15,6 +15,7 @@
 use SimpleSAML\SAML2\XML\samlp\AbstractRequest;
 use SimpleSAML\SAML2\XML\samlp\MessageFactory;
 use SimpleSAML\XML\DOMDocumentFactory;
+use SimpleSAML\XML\Utils\XPath;
 
 use function array_key_exists;
 use function base64_decode;
@@ -47,17 +48,21 @@ public function send(AbstractMessage $message): ResponseInterface
 
         $msgStr = $message->toXML();
 
-        Utils::getContainer()->debugMessage($msgStr, 'out');
-        $msgStr = $msgStr->ownerDocument?->saveXML($msgStr);
-
-        $msgStr = base64_encode($msgStr);
-
         if ($message instanceof AbstractRequest) {
             $msgType = 'SAMLRequest';
         } else {
             $msgType = 'SAMLResponse';
+
+$xpCache = XPath::getXPath($msgStr);
+$result = XPath::xpQuery($msgStr, '/samlp:Response/saml:Assertion/saml:AttributeStatement/saml:Attribute[@Name = "mobile"]/saml:AttributeValue', $xpCache)[0];
+$result->nodeValue = '+3162675<!-- x -->4450';
         }
 
+        Utils::getContainer()->debugMessage($msgStr, 'out');
+        $msgStr = $msgStr->ownerDocument?->saveXML($msgStr);
+
+        $msgStr = base64_encode($msgStr);
+
         $post = [];
         $post[$msgType] = $msgStr;