diff --git a/api/components/OAuth2/Entities/RefreshTokenEntity.php b/api/components/OAuth2/Entities/RefreshTokenEntity.php
index 372f003..eec5987 100644
--- a/api/components/OAuth2/Entities/RefreshTokenEntity.php
+++ b/api/components/OAuth2/Entities/RefreshTokenEntity.php
@@ -15,7 +15,7 @@ class RefreshTokenEntity extends \League\OAuth2\Server\Entity\RefreshTokenEntity
         return false;
     }
 
-    public function getSession(): SessionEntity {
+    public function getSession(): ?SessionEntity {
         if ($this->session instanceof SessionEntity) {
             return $this->session;
         }