diff --git a/plone/formwidget/captcha/captcha_input.pt b/plone/formwidget/captcha/captcha_input.pt
index e118a4f..f925634 100644
--- a/plone/formwidget/captcha/captcha_input.pt
+++ b/plone/formwidget/captcha/captcha_input.pt
@@ -4,4 +4,4 @@
   <a href="" target="_blank"
     tal:attributes="href view/captchaAudio">Listen to audio for this captcha</a>
 </div>
-<input id="form-widgets-captcha" class="text-widget textline-field" type="text" value="" name="form.widgets.captcha"/>
\ No newline at end of file
+<input id="form-widgets-captcha" class="text-widget required textline-field" type="text" value="" name="form.widgets.captcha"/>
\ No newline at end of file