diff --git a/phpgwapi/inc/class.categories.inc.php b/phpgwapi/inc/class.categories.inc.php
index 9a17d0e3ca..c1a821f2b3 100644
--- a/phpgwapi/inc/class.categories.inc.php
+++ b/phpgwapi/inc/class.categories.inc.php
@@ -482,7 +482,11 @@ class categories
 	function check_list($needed, $cat_list)
  	{
 		if (empty($cat_list)) return $cat_list;
-
+		if (is_array($cat_list))
+		{
+			$cat_list = implode(',',$cat_list);
+			//error_log(__METHOD__.__LINE__.' string expected, array found for cat_list. Converted to:'.$cat_list);
+		}
 		$cat_arr = explode(',',$cat_list);
 		if (!empty($cat_arr) && is_array($cat_arr) && count($cat_arr) > 0)
 		{