diff --git a/plinth/modules/quassel/__init__.py b/plinth/modules/quassel/__init__.py
index aa85d5588..200f64509 100644
--- a/plinth/modules/quassel/__init__.py
+++ b/plinth/modules/quassel/__init__.py
@@ -50,3 +50,13 @@ def is_enabled():
 def is_running():
     """Return whether the service is running."""
     return action_utils.service_is_running('quasselcore')
+
+
+def diagnose():
+    """Run diagnostics and return the results."""
+    results = []
+
+    results.append(action_utils.diagnose_port_listening(4242, 'tcp4'))
+    results.append(action_utils.diagnose_port_listening(4242, 'tcp6'))
+
+    return results
diff --git a/plinth/modules/quassel/templates/quassel.html b/plinth/modules/quassel/templates/quassel.html
index 14d54c046..63575476b 100644
--- a/plinth/modules/quassel/templates/quassel.html
+++ b/plinth/modules/quassel/templates/quassel.html
@@ -47,6 +47,9 @@
     {% endif %}
   </p>
 
+  {% include "diagnostics_button.html" with module="quassel" %}
+
+
   <h3>{% trans "Configuration" %}</h3>
 
   <form class="form" method="post">