diff --git a/plinth/modules/quassel/forms.py b/plinth/modules/quassel/forms.py
index 723f7338e..76c75b357 100644
--- a/plinth/modules/quassel/forms.py
+++ b/plinth/modules/quassel/forms.py
@@ -24,4 +24,5 @@ class QuasselForm(AppForm):
         help_text=_(
             'Select a domain to use TLS with. If the list is empty, please '
             'configure at least one domain with certificates.'),
+        required=False,
     )
diff --git a/plinth/modules/quassel/views.py b/plinth/modules/quassel/views.py
index bf7337f03..cad5ed3de 100644
--- a/plinth/modules/quassel/views.py
+++ b/plinth/modules/quassel/views.py
@@ -20,7 +20,9 @@ class QuasselAppView(AppView):
     def form_valid(self, form):
         """Change the access control of Radicale service."""
         data = form.cleaned_data
-        if quassel.get_domain() != data['domain']:
+        app_disable = form.initial['is_enabled'] and not data['is_enabled']
+
+        if not app_disable and quassel.get_domain() != data['domain']:
             quassel.set_domain(data['domain'])
             quassel.app.get_component(
                 'letsencrypt-quassel').setup_certificates()