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
@@ -710,6 +710,7 @@
     initialContentEncryptedMessage: t.String,
     initialNotificationsEncryptedMessage: t.String,
     doNotRegister: t.Boolean,
+    source: t.maybe(t.enums.of(values(logInActionSources))),
   });
 
 async function keyserverAuthResponder(