diff --git a/defense.php b/defense.php
index a92fb53..e5cb156 100644
--- a/defense.php
+++ b/defense.php
@@ -42,7 +42,7 @@ class defense extends rcube_plugin {
     private function isIPinArray($ip, $array) {
         foreach ($array as $value) {
             if ((strpos($value, '/') === false) && ($ip == $value)) { return true; }
-            if (isIPinCIDR($ip, $value)) { return true; }
+            if (%this->isIPinCIDR($ip, $value)) { return true; }
         }
         return false;
     }