diff --git a/keyserver/src/socket/session-utils.js b/keyserver/src/socket/session-utils.js
--- a/keyserver/src/socket/session-utils.js
+++ b/keyserver/src/socket/session-utils.js
@@ -31,6 +31,7 @@
   type ServerCheckStateServerRequest,
 } from 'lib/types/request-types.js';
 import { sessionCheckFrequency } from 'lib/types/session-types.js';
+import { signedIdentityKeysBlobValidator } from 'lib/utils/crypto-utils.js';
 import { hash } from 'lib/utils/objects.js';
 import { promiseAll } from 'lib/utils/promises.js';
 import {
@@ -120,6 +121,13 @@
     ),
     keys: t.list(t.String),
   }),
+  tShape({
+    type: t.irreducible(
+      'serverRequestTypes.SIGNED_IDENTITY_KEYS_BLOB',
+      x => x === serverRequestTypes.SIGNED_IDENTITY_KEYS_BLOB,
+    ),
+    signedIdentityKeysBlob: signedIdentityKeysBlobValidator,
+  }),
 ]);
 
 type StateCheckStatus =