diff --git a/core/admin/assets/app.js b/core/admin/assets/app.js
index dc3414f2..5df8052c 100644
--- a/core/admin/assets/app.js
+++ b/core/admin/assets/app.js
@@ -66,5 +66,12 @@ $('document').ready(function() {
     // init clipboard.js
     new ClipboardJS('.btn-clip');
 
+    // disable login if not possible
+    var l = $('#login_needs_https');
+    if (l.length && window.location.protocol != 'https:') {
+        l.removeClass("d-none");
+        $('form :input').prop('disabled', true);
+    }
+
 });
 
diff --git a/core/admin/mailu/ui/templates/login.html b/core/admin/mailu/ui/templates/login.html
index 118173cb..4c38d134 100644
--- a/core/admin/mailu/ui/templates/login.html
+++ b/core/admin/mailu/ui/templates/login.html
@@ -8,14 +8,11 @@
 {% trans %}to access the administration tools{% endtrans %}
 {%- endblock %}
 
-{%+ block content %}
 {% if config["SESSION_COOKIE_SECURE"] %}
-<script language="javascript">
-	if(window.location.protocol != "https:") {
-		document.write('<div class="alert alert-danger" role="alert">The login form has been disabled as <b>SESSION_COOKIE_SECURE</b> is on but you are accessing Mailu over HTTP</div>');
-		window.stop();
-	}
-</script>
-{% endif %}
+{%- block content %}
+<div id="login_needs_https" class="alert alert-danger d-none" role="alert">
+{% trans %}The login form has been disabled as <b>SESSION_COOKIE_SECURE</b> is on but you are accessing Mailu over HTTP.{% endtrans %}
+</div>
 {{ super() }}
-{%+ endblock %}
+{%- endblock %}
+{% endif %}