diff --git a/plinth/modules/first_boot/templates/firstboot_welcome.html b/plinth/modules/first_boot/templates/firstboot_welcome.html
index eaee1b874..20cd4092e 100644
--- a/plinth/modules/first_boot/templates/firstboot_welcome.html
+++ b/plinth/modules/first_boot/templates/firstboot_welcome.html
@@ -17,7 +17,7 @@ no-brand
          src="{% static 'theme/img/freedombox-logo-standard.svg' %}"/>
   </div>
 
-  <form class="form text-center" method="post">
+  <form class="form form-start text-center" method="post">
     {% csrf_token %}
 
     {% if show_wizard_password_prompt %}
diff --git a/plinth/tests/functional/__init__.py b/plinth/tests/functional/__init__.py
index 92e35ad02..ad20a0b9c 100644
--- a/plinth/tests/functional/__init__.py
+++ b/plinth/tests/functional/__init__.py
@@ -287,7 +287,7 @@ def login_with_account(browser, url, username, password=None):
             submit(browser)
     else:
         browser.visit(base_url + '/plinth/firstboot/welcome')
-        submit(browser)  # click the "Start Setup" button
+        submit(browser, form_class='form-start')  # "Start Setup" button
         _create_admin_account(browser, username, password)
         if '/network-topology-first-boot' in browser.url:
             submit(browser, element=browser.find_by_name('skip')[0])