diff --git a/CRM/Case/XMLProcessor.php b/CRM/Case/XMLProcessor.php
index b01695be104d..4b72ad0f18a6 100644
--- a/CRM/Case/XMLProcessor.php
+++ b/CRM/Case/XMLProcessor.php
@@ -83,7 +83,7 @@ public static function mungeCaseType($caseType) {
    *
    * @return array
    */
-  public function &allActivityTypes($indexName = TRUE, $all = FALSE) {
+  public static function allActivityTypes($indexName = TRUE, $all = FALSE) {
     if (self::$activityTypes === NULL) {
       self::$activityTypes = CRM_Case_PseudoConstant::caseActivityType($indexName, $all);
     }