diff --git a/lib/server/server.js b/lib/server/server.js
index 7ca679f0d5..87a59d9dc2 100644
--- a/lib/server/server.js
+++ b/lib/server/server.js
@@ -307,7 +307,7 @@ function execute(port, options) {
     }
   });
 
-  app.get(/main\.css$/, (req, res) => {
+  app.get(`${siteConfig.baseUrl}css/main.css`, (req, res) => {
     const mainCssPath = join(
       __dirname,
       '..',