diff --git a/rules_shipping_framework_joomla.php b/rules_shipping_framework_joomla.php
index eeb6f71d7dfcc0f56a2eaf910d08cebc90c76526..eea9dec844049107593e9f6c9bc86533bf6a44d1 100644
--- a/rules_shipping_framework_joomla.php
+++ b/rules_shipping_framework_joomla.php
@@ -37,7 +37,11 @@ class RulesShippingFrameworkJoomla extends RulesShippingFramework {
 		//          ...);
 		JPluginHelper::importPlugin('vmshipmentrules');
 		$dispatcher = JDispatcher::getInstance();
-		$custfuncdefs = call_user_func_array('array_merge', $dispatcher->trigger('onVmShippingRulesRegisterCustomFunctions',array()));
+		$defs = $dispatcher->trigger('onVmShippingRulesRegisterCustomFunctions',array());
+		$custfuncdefs = array();
+		if (!empty($defs)) {
+			$custfuncdefs = call_user_func_array('array_merge', $defs);
+		}
 		$custfuncdefs['convertfromcurrency'] = array($this, 'convert_from_currency');
 		$custfuncdefs['converttocurrency'] = array($this, 'convert_to_currency');