diff --git a/packages/core/admin/admin/src/pages/AuthPage/components/Register/index.js b/packages/core/admin/admin/src/pages/AuthPage/components/Register/index.js
index cec300e4db..6b74f850c6 100644
--- a/packages/core/admin/admin/src/pages/AuthPage/components/Register/index.js
+++ b/packages/core/admin/admin/src/pages/AuthPage/components/Register/index.js
@@ -113,7 +113,7 @@ const Register = ({ authType, fieldsToDisable, noSignin, onSubmit, schema }) =>
           enableReinitialize
           initialValues={{
             firstname: userInfo.firstname || '',
-            lastname: userInfo.lastname || '',
+            lastname: userInfo.lastname || undefined,
             email: userInfo.email || '',
             password: '',
             confirmPassword: '',