diff --git a/filegateway/session_pool.js b/filegateway/session_pool.js
index 416b036..678b69e 100644
--- a/filegateway/session_pool.js
+++ b/filegateway/session_pool.js
@@ -61,7 +61,7 @@ class SessionPool {
     for (const [key, session] of this.sessions) {
       if (session.expiration <= now) {
         this.sessions.delete(key);
-        session.off(session)
+        session.off(session.value)
       }
     }
   }