diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -292,7 +292,7 @@
       loggedInUserInfoValidator,
     ]),
     cookieChange: tShape({
-      threadInfos: t.dict(t.String, rawThreadInfoValidator),
+      threadInfos: t.dict(tID, rawThreadInfoValidator),
       userInfos: t.list(userInfoValidator),
     }),
   });