diff --git a/wp-caliper-event-hooks.php b/wp-caliper-event-hooks.php
index 46eb7a7..896fbb1 100644
--- a/wp-caliper-event-hooks.php
+++ b/wp-caliper-event-hooks.php
@@ -443,7 +443,7 @@ function wp_caliper_add_attachment( $post_id ) {
  * @param bool     $user_login user login.
  * @param \WP_USER $user WordPress user object.
  */
-function wp_caliper_wp_login( $user_login, $user ) {
+function wp_caliper_wp_login( $user_login = false, $user = false ) {
 	if ( empty( $user->ID ) ) {
 		return;
 	}