diff --git a/includes/event/event-date.php b/includes/event/event-date.php
index 75032d8b..f5d20550 100644
--- a/includes/event/event-date.php
+++ b/includes/event/event-date.php
@@ -17,7 +17,7 @@
  */
 abstract class Event_Date extends DateTimeImmutable {
 	protected $event_timezone;
-	public function __construct( string $date, DateTimeZone $timezone = null ) {
+	public function __construct( string $date, ?DateTimeZone $timezone = null ) {
 		if ( ! $timezone ) {
 			$timezone = new DateTimeZone( 'UTC' );
 		}
diff --git a/includes/event/event.php b/includes/event/event.php
index 42879155..c013ccf1 100644
--- a/includes/event/event.php
+++ b/includes/event/event.php
@@ -9,25 +9,25 @@
 use Wporg\TranslationEvents\Translation_Events;
 
 class InvalidTimeZone extends Exception {
-	public function __construct( Throwable $previous = null ) {
+	public function __construct( ?Throwable $previous = null ) {
 		parent::__construct( 'Event time zone is invalid', 0, $previous );
 	}
 }
 
 class InvalidStart extends Exception {
-	public function __construct( Throwable $previous = null ) {
+	public function __construct( ?Throwable $previous = null ) {
 		parent::__construct( 'Event start is invalid', 0, $previous );
 	}
 }
 
 class InvalidEnd extends Exception {
-	public function __construct( Throwable $previous = null ) {
+	public function __construct( ?Throwable $previous = null ) {
 		parent::__construct( 'Event end is invalid', 0, $previous );
 	}
 }
 
 class InvalidStatus extends Exception {
-	public function __construct( Throwable $previous = null ) {
+	public function __construct( ?Throwable $previous = null ) {
 		parent::__construct( 'Event status is invalid', 0, $previous );
 	}
 }
@@ -58,7 +58,7 @@ public function __construct(
 		string $status,
 		string $title,
 		string $description,
-		DateTimeImmutable $updated_at = null,
+		?DateTimeImmutable $updated_at = null,
 		string $attendance_mode = 'onsite'
 	) {
 		$this->author_id = $author_id;
@@ -184,7 +184,7 @@ public function set_description( string $description ): void {
 		$this->description = $description;
 	}
 
-	public function set_updated_at( DateTimeImmutable $updated_at = null ): void {
+	public function set_updated_at( ?DateTimeImmutable $updated_at = null ): void {
 		$this->updated_at = $updated_at ?? Translation_Events::now();
 	}
 
diff --git a/includes/routes/user/attend-event.php b/includes/routes/user/attend-event.php
index a739601b..313811d2 100644
--- a/includes/routes/user/attend-event.php
+++ b/includes/routes/user/attend-event.php
@@ -38,11 +38,10 @@ public function handle( int $event_id ): void {
 				$this->die_with_error( esc_html__( 'You are not authorized to change the attendance mode of this attendee', 'gp-translation-events' ), 403 );
 			}
 		}
-		$user = wp_get_current_user();
-		if ( ! $user ) {
+		$user_id = get_current_user_id();
+		if ( ! $user_id ) {
 			$this->die_with_error( esc_html__( 'Only logged-in users can attend events', 'gp-translation-events' ), 403 );
 		}
-		$user_id = $user->ID;
 
 		$event = $this->event_repository->get_event( $event_id );
 		if ( ! $event ) {