diff --git a/ui/sign-in/src/SignInPage.tsx b/ui/sign-in/src/SignInPage.tsx
index 502feec..a1339c3 100644
--- a/ui/sign-in/src/SignInPage.tsx
+++ b/ui/sign-in/src/SignInPage.tsx
@@ -103,6 +103,10 @@ export function SignInPage() {
   const handleRegister = async (e: FormEvent) => {
     e.preventDefault();
     setError(null);
+    if (!identifier.includes('@')) {
+      setError('Please enter a valid email address');
+      return;
+    }
     if (password !== confirmPassword) {
       setError('Passwords do not match');
       return;