diff --git a/keyserver/src/responders/siwe-nonce-responders.js b/keyserver/src/responders/siwe-nonce-responders.js
--- a/keyserver/src/responders/siwe-nonce-responders.js
+++ b/keyserver/src/responders/siwe-nonce-responders.js
@@ -7,14 +7,18 @@
 import { tShape } from 'lib/utils/validation-utils.js';
 
 import { createSIWENonceEntry } from '../creators/siwe-nonce-creator.js';
+import type { Viewer } from '../session/viewer.js';
+import { validateOutput } from '../utils/validation-utils.js';
 
 export const siweNonceResponseValidator: TInterface<SIWENonceResponse> =
   tShape<SIWENonceResponse>({ nonce: t.String });
 
-async function siweNonceResponder(): Promise<SIWENonceResponse> {
+async function siweNonceResponder(viewer: Viewer): Promise<SIWENonceResponse> {
   const generatedNonce = generateNonce();
   await createSIWENonceEntry(generatedNonce);
-  return { nonce: generatedNonce };
+  return validateOutput(viewer.platformDetails, siweNonceResponseValidator, {
+    nonce: generatedNonce,
+  });
 }
 
 export { siweNonceResponder };