diff --git a/odoo/service/server.py b/odoo/service/server.py
index b4f3dca6c1b..9bbbc627a42 100644
--- a/odoo/service/server.py
+++ b/odoo/service/server.py
@@ -952,6 +952,9 @@ def start(preload=None, stop=False):
     if odoo.evented:
         server = GeventServer(odoo.service.wsgi_server.application)
     elif config['workers']:
+        if config['test_enable'] or config['test_file']:
+            _logger.warning("Unit testing in workers mode could fail; use --workers 0.")
+
         server = PreforkServer(odoo.service.wsgi_server.application)
     else:
         server = ThreadedServer(odoo.service.wsgi_server.application)