diff --git a/addons/web/controllers/main.py b/addons/web/controllers/main.py
index 930dde340ed..ff3224fafbc 100644
--- a/addons/web/controllers/main.py
+++ b/addons/web/controllers/main.py
@@ -178,11 +178,11 @@ def module_installed_bypass_session(dbname):
     return {}
 
 def module_boot(db=None):
-    server_wide_modules = {'base', 'web'} | set(odoo.conf.server_wide_modules)
-    serverside = []
+    server_wide_modules = odoo.conf.server_wide_modules or []
+    serverside = ['base', 'web']
     dbside = []
     for i in server_wide_modules:
-        if i in http.addons_manifest:
+        if i in http.addons_manifest and i not in serverside:
             serverside.append(i)
     monodb = db or db_monodb()
     if monodb: