diff --git a/phpgwapi/inc/class.common.inc.php b/phpgwapi/inc/class.common.inc.php
index ba6e6b427b..fbddda46b1 100644
--- a/phpgwapi/inc/class.common.inc.php
+++ b/phpgwapi/inc/class.common.inc.php
@@ -281,18 +281,17 @@ class common
 	 */
 	static function randomstring($size)
 	{
-		$s = '';
-		srand((double)microtime()*1000000);
-		$random_char = array(
+		static $random_char = array(
 			'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f',
 			'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v',
 			'w','x','y','z','A','B','C','D','E','F','G','H','I','J','K','L',
 			'M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
 		);
 
-		for ($i=0; $i<$size; $i++)
+		$s = '';
+		for ($i=0; $i < $size; $i++)
 		{
-			$s .= $random_char[rand(1,61)];
+			$s .= $random_char[mt_rand(0,count($random_char)-1)];
 		}
 		return $s;
 	}