diff --git a/example/rp/index.html b/example/rp/index.html
index c3fa2e9f208c6b5398e749a2b3ad2602f478eb1f..16c540bcd1411dd88c8bb5d49d22b2c6a647fa6f 100644
--- a/example/rp/index.html
+++ b/example/rp/index.html
@@ -171,6 +171,12 @@ $(document).ready(function() {
   $(".specify button.assertion").click(function() {
     var requiredEmail = $.trim($('#requiredEmail').val());
     if (!requiredEmail.length) requiredEmail = undefined;
+    if (requiredEmail.indexOf('@') === -1) {
+      alert('Invalid Email in "Require a specific email" field. Adding @example.com');
+      $('#requiredEmail').val(requiredEmail + '@example.com');
+      $('#requiredEmail').focus();
+      return;
+    }
 
     $(".specify button.assertion").attr('disabled', 'true');