diff --git a/searx/preferences.py b/searx/preferences.py
index b37f0104..a9f16ff7 100644
--- a/searx/preferences.py
+++ b/searx/preferences.py
@@ -397,11 +397,13 @@ class Preferences:
                 choices=['', 'logicodev', 'logicodev-dark', 'pointhi']),
             'advanced_search': MapSetting(
                 settings['ui'].get('advanced_search', False),
+                is_locked('advanced_search'),
                 map={
                     '0': False,
                     '1': True,
                     'False': False,
-                    'True': True
+                    'True': True,
+                    'on': True,
                 }
             ),
         }
diff --git a/searx/webapp.py b/searx/webapp.py
index c0530a83..b1fa84ce 100755
--- a/searx/webapp.py
+++ b/searx/webapp.py
@@ -546,7 +546,7 @@ def index():
     """Render index page."""
 
     # UI
-    advanced_search = request.form.get('advanced_search', request.preferences.get_value('advanced_search'))
+    advanced_search = request.preferences.get_value('advanced_search')
 
     # redirect to search if there's a query in the request
     if request.form.get('q'):
@@ -611,7 +611,7 @@ def search():
         return redirect(result_container.redirect_url)
 
     # UI
-    advanced_search = request.form.get('advanced_search', None)
+    advanced_search = request.preferences.get_value('advanced_search')
 
     # Server-Timing header
     request.timings = result_container.get_timings()