diff --git a/includes/Models/PriorityQueue.php b/includes/Models/PriorityQueue.php
index 9fd0a2b..ac2b52a 100644
--- a/includes/Models/PriorityQueue.php
+++ b/includes/Models/PriorityQueue.php
@@ -13,7 +13,7 @@ class PriorityQueue extends \SplPriorityQueue {
 	 * @param mixed $priority2 Second Priority Queue
 	 * @return int
 	 */
-	public function compare( $priority1, $priority2 ) {
+	public function compare( $priority1, $priority2 ) : int {
 		if ( $priority1 === $priority2 ) {
 			return 0;
 		}