diff --git a/php/OAuthSimple.php b/php/OAuthSimple.php
index ff57933..df89050 100644
--- a/php/OAuthSimple.php
+++ b/php/OAuthSimple.php
@@ -344,7 +344,7 @@ class OAuthSimple {
     }
 
     function _getTimeStamp() {
-        return $this->_parameters['stamp'] = time();
+        return $this->_parameters['oauth_timestamp'] = time();
     }
 
     function _normalizedParameters() {