diff --git a/odoo/tools/config.py b/odoo/tools/config.py
index 0f4c0d0761d..5e406d036f2 100644
--- a/odoo/tools/config.py
+++ b/odoo/tools/config.py
@@ -394,6 +394,9 @@ class configmanager(object):
         # the same for the pidfile
         if self.options['pidfile'] in ('None', 'False'):
             self.options['pidfile'] = False
+        # the same for the test_tags
+        if self.options['test_tags'] == 'None':
+            self.options['test_tags'] = None
         # and the server_wide_modules
         if self.options['server_wide_modules'] in ('', 'None', 'False'):
             self.options['server_wide_modules'] = 'base,web'