diff --git a/resources/auth_css_theme.xml b/resources/auth_css_theme.xml
index 6140156..6c51449 100644
--- a/resources/auth_css_theme.xml
+++ b/resources/auth_css_theme.xml
@@ -80,8 +80,8 @@
 
   <message id="Wt.Auth.template.registration">
     <div class="Wt-form Wt-auth-registration">
-      <h2 class="is-hidden">${tr:Wt.Auth.registration-form-title}</h2>
-      <p class="is-hidden">${tr:Wt.Auth.registration-form-info}</p>
+      <h2 class="bulma-is-hidden">${tr:Wt.Auth.registration-form-title}</h2>
+      <p class="bulma-is-hidden">${tr:Wt.Auth.registration-form-info}</p>
 
       ${password-description}