diff --git a/Captcha.php b/Captcha.php
index c6a05b1c9..995feb478 100644
--- a/Captcha.php
+++ b/Captcha.php
@@ -41,6 +41,7 @@ class SimpleCaptcha {
 		return "<p><label for=\"wpCaptchaWord\">{$captcha['question']} = </label>" .
 			Xml::element( 'input', array(
 				'name' => 'wpCaptchaWord',
+				'class' => 'mw-ui-input',
 				'id'   => 'wpCaptchaWord',
 				'size'  => 5,
 				'autocomplete' => 'off',
diff --git a/FancyCaptcha.class.php b/FancyCaptcha.class.php
index e2dbb82bb..46387c9e2 100644
--- a/FancyCaptcha.class.php
+++ b/FancyCaptcha.class.php
@@ -130,6 +130,7 @@ class FancyCaptcha extends SimpleCaptcha {
 			) .
 			Html::element( 'input', array(
 					'name' => 'wpCaptchaWord',
+					'class' => 'mw-ui-input',
 					'id'   => 'wpCaptchaWord',
 					'type' => 'text',
 					'size' => '12',  // max_length in captcha.py plus fudge factor
diff --git a/QuestyCaptcha.class.php b/QuestyCaptcha.class.php
index 3acfa46e0..a7ab37b8f 100644
--- a/QuestyCaptcha.class.php
+++ b/QuestyCaptcha.class.php
@@ -43,6 +43,7 @@ class QuestyCaptcha extends SimpleCaptcha {
 			Html::element( 'input', array(
 				'name' => 'wpCaptchaWord',
 				'id'   => 'wpCaptchaWord',
+				'class' => 'mw-ui-input',
 				'required',
 				'autocomplete' => 'off',
 				'tabindex' => 1 ) ) . // tab in before the edit textarea