diff --git a/passkeys-backend/functions/registration/start.js b/passkeys-backend/functions/registration/start.js
index 5b8e7980..1d946b7f 100644
--- a/passkeys-backend/functions/registration/start.js
+++ b/passkeys-backend/functions/registration/start.js
@@ -35,9 +35,12 @@ exports.handler = async (context, event, callback) => {
         name: 'PasskeySample',
         origins: [
           `https://${RELYING_PARTY}`,
-          ...(ANDROID_APP_KEYS.split(',') || []),
+          ...(ANDROID_APP_KEYS?.split(',') ?? []),
         ],
       },
+      user: {
+        display_name: event.username,
+      },
       authenticator_criteria: {
         authenticator_attachment: 'platform',
         discoverable_credentials: 'preferred',
diff --git a/passkeys-backend/tests/registration-start.test.js b/passkeys-backend/tests/registration-start.test.js
index 097df955..634a8ad6 100644
--- a/passkeys-backend/tests/registration-start.test.js
+++ b/passkeys-backend/tests/registration-start.test.js
@@ -1,9 +1,13 @@
+/* eslint-disable camelcase */
+
 const axios = require('axios');
 const helpers = require('../../test/test-helper');
 
 jest.mock('axios');
 
 const mockContext = {
+  API_URL: 'https://api.com',
+  RELYING_PARTY: 'example.com',
   ANDROID_APP_KEYS: 'key1,key2,key3',
   getTwilioClient: () => ({
     username: 'mockUsername',
@@ -11,6 +15,28 @@ const mockContext = {
   }),
 };
 
+const mockRequestBody = {
+  friendly_name: 'Passkey Example',
+  to: {
+    user_identifier: 'user001',
+  },
+  content: {
+    relying_party: {
+      id: 'example.com',
+      name: 'PasskeySample',
+      origins: [`https://example.com`],
+    },
+    user: {
+      display_name: 'user001',
+    },
+    authenticator_criteria: {
+      authenticator_attachment: 'platform',
+      discoverable_credentials: 'preferred',
+      user_verification: 'preferred',
+    },
+  },
+};
+
 describe('registration/start', () => {
   beforeAll(() => {
     jest.clearAllMocks();
@@ -52,12 +78,48 @@ describe('registration/start', () => {
       done();
     };
 
+    handlerFunction(mockContext, { username: 'user001' }, callback);
+  });
+
+  it('works with empty ANDROID_APP_KEYS', (done) => {
+    const callback = (_, { _body }) => {
+      expect(axios.post).toHaveBeenCalledWith(
+        'https://api.com/Factors',
+        mockRequestBody,
+        { auth: { password: 'mockPassword', username: 'mockUsername' } }
+      );
+      done();
+    };
+
+    const mockContextWithoutAndroidKeys = {
+      API_URL: 'https://api.com',
+      RELYING_PARTY: 'example.com',
+      getTwilioClient: () => ({
+        username: 'mockUsername',
+        password: 'mockPassword',
+      }),
+    };
+
     handlerFunction(
-      mockContext,
-      {
-        username: 'test-username',
-      },
+      mockContextWithoutAndroidKeys,
+      { username: 'user001' },
       callback
     );
   });
+
+  it('calls the API with the expected request body', (done) => {
+    const modifiedRequest = structuredClone(mockRequestBody);
+    modifiedRequest.content.relying_party.origins.push('key1', 'key2', 'key3');
+
+    const callback = (_, result) => {
+      expect(axios.post).toHaveBeenCalledWith(
+        'https://api.com/Factors',
+        modifiedRequest,
+        { auth: { password: 'mockPassword', username: 'mockUsername' } }
+      );
+      done();
+    };
+
+    handlerFunction(mockContext, { username: 'user001' }, callback);
+  });
 });