diff --git a/includes/core/classes/class-rsvp.php b/includes/core/classes/class-rsvp.php
index 4da755339..0797428f7 100644
--- a/includes/core/classes/class-rsvp.php
+++ b/includes/core/classes/class-rsvp.php
@@ -277,7 +277,7 @@ public function save( int $user_id, string $status, int $anonymous = 0, int $gue
 			'anonymous' => intval( $anonymous ),
 		);
 
-		wp_cache_delete( sprintf( self::CACHE_KEY, $post_id ) );
+		wp_cache_delete( sprintf( self::CACHE_KEY, $post_id ), '' );
 
 		if ( ! $limit_reached ) {
 			$this->check_waiting_list();
@@ -383,7 +383,7 @@ public function attending_limit_reached( array $current_response, int $guests =
 	public function responses(): array {
 		$post_id    = $this->event->ID;
 		$cache_key  = sprintf( self::CACHE_KEY, $post_id );
-		$retval     = wp_cache_get( $cache_key );
+		$retval     = wp_cache_get( $cache_key, '' );
 		$rsvp_query = Rsvp_Query::get_instance();
 
 		// @todo add testing with cache.
@@ -496,7 +496,7 @@ static function ( $response ) use ( $status ) {
 			$retval[ $status ]['count']     = count( $retval[ $status ]['responses'] ) + $guests;
 		}
 
-		wp_cache_set( $cache_key, $retval, 15 * MINUTE_IN_SECONDS );
+		wp_cache_set( $cache_key, $retval, '', 15 * MINUTE_IN_SECONDS );
 
 		return $retval;
 	}