diff --git a/lib/Hook/hook.extends.class.php b/lib/Hook/hook.extends.class.php
index bf5bc03e2..fd53543cb 100644
--- a/lib/Hook/hook.extends.class.php
+++ b/lib/Hook/hook.extends.class.php
@@ -19,7 +19,7 @@ Class GML_Hook extends Hook {
 
         $args = $this->getArguments($argsNumber, $args);
 
-        if (! ($class && $method) && function_exists($function)) {
+        if (! ($class && $method) && is_callable($function)) {
             return call_user_func_array($function, $args);
         } elseif ($obj = call_user_func(array($class, $this->singleton))) {
             if ($obj !== false) {
@@ -161,4 +161,4 @@ Class GML_Hook extends Hook {
     }
 }
 
-// end  Hook Class;
\ No newline at end of file
+// end  Hook Class;