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
@@ -43,6 +43,7 @@
   getPublicKeyFromSIWEStatement,
   isValidSIWEMessage,
   isValidSIWEStatementWithPublicKey,
+  primaryIdentityPublicKeyRegex,
 } from 'lib/utils/siwe-utils.js';
 import {
   tShape,
@@ -50,6 +51,7 @@
   tPassword,
   tEmail,
   tOldValidUsername,
+  tRegex,
 } from 'lib/utils/validation-utils';
 
 import {
@@ -302,6 +304,7 @@
   deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
   platformDetails: tPlatformDetails,
   source: t.maybe(t.enums.of(values(logInActionSources))),
+  primaryIdentityPublicKey: t.maybe(tRegex(primaryIdentityPublicKeyRegex)),
 });
 
 async function logInResponder(
diff --git a/lib/utils/siwe-utils.js b/lib/utils/siwe-utils.js
--- a/lib/utils/siwe-utils.js
+++ b/lib/utils/siwe-utils.js
@@ -102,6 +102,7 @@
   siweStatementWithoutPublicKey,
   isValidSIWENonce,
   isValidEthereumAddress,
+  primaryIdentityPublicKeyRegex,
   isValidPrimaryIdentityPublicKey,
   createSIWEMessage,
   isValidSIWEMessage,