diff --git a/lib/Entities/StatisticsWooCommercePurchaseEntity.php b/lib/Entities/StatisticsWooCommercePurchaseEntity.php
index d9027bd57a..b26db81f1c 100644
--- a/lib/Entities/StatisticsWooCommercePurchaseEntity.php
+++ b/lib/Entities/StatisticsWooCommercePurchaseEntity.php
@@ -108,7 +108,7 @@ class StatisticsWooCommercePurchaseEntity {
   /**
    * @return int
    */
-  public function getOrderId() {
+  public function getOrderId(): int {
     return $this->orderId;
   }