diff --git a/templates/themes/categories/theme.php b/templates/themes/categories/theme.php
index 86bfa023..22a0905d 100644
--- a/templates/themes/categories/theme.php
+++ b/templates/themes/categories/theme.php
@@ -148,7 +148,7 @@
             return $stats;
         }
 
-        private static function countUniqueIps($markAsCounted, $timespan, $_board) {
+        private static function countUniqueIps(&$markAsCounted, $timespan, $_board) {
         	$unique_query = query(
             	sprintf("SELECT DISTINCT ip FROM ``posts_%s`` WHERE time > %d",
                             $_board['uri'],