diff --git a/core/event_api.php b/core/event_api.php
index 57a383ec8d..0e968a79cf 100644
--- a/core/event_api.php
+++ b/core/event_api.php
@@ -215,7 +215,7 @@ function event_callback( $p_event, $p_callback, $p_plugin, $p_params = null ) {
  * @return void
  * @access public
  */
-function event_type_execute( $p_event, array $p_callbacks, array $p_params ) {
+function event_type_execute( $p_event, array $p_callbacks, array $p_params = null ) {
 	foreach( $p_callbacks as $t_plugin => $t_callbacks ) {
 		foreach( $t_callbacks as $t_callback ) {
 			event_callback( $p_event, $t_callback, $t_plugin, $p_params );
@@ -275,7 +275,7 @@ function event_type_output( $p_event, array $p_callbacks, $p_params = null ) {
  * @return string Output string
  * @access public
  */
-function event_type_chain( $p_event, array $p_callbacks, $p_input, array $p_params ) {
+function event_type_chain( $p_event, array $p_callbacks, $p_input, array $p_params = null) {
 	$t_output = $p_input;
 
 	foreach( $p_callbacks as $t_plugin => $t_callbacks ) {