diff --git a/lib/css.js b/lib/css.js
index 4174b3d76..ced8eed52 100644
--- a/lib/css.js
+++ b/lib/css.js
@@ -1,50 +1,51 @@
 'use strict';
 
 const fs = require('fs');
 const preq = require('preq');
 const mUtil = require('./mobile-util');
 const mwapi = require('./mwapi');
 
 const pageLibJs = require.resolve('wikimedia-page-library');
 // HACK: Get the corresponding .css file to the pagelib main .js file by swapping the file extension
 const pageLibCss = pageLibJs.replace(/\.js$/, '.css');
 
 const SITE_MODULES = [ 'mobile.site.styles' ];
 
 function load(modules, domain = 'en.wikipedia.org', lang = 'en') {
     const modList = modules.join('|');
     return preq.get(`https://${domain}/w/load.php?debug=false&lang=${lang}&skin=minerva&target=mobile&only=styles&modules=${modList}`);
 }
 
 function respond(res, css) {
     res.status(200);
     mUtil.setContentType(res, mUtil.CONTENT_TYPES.css);
     mUtil.setETag(res, mUtil.hashCode(css));
     res.set('Cache-Control', 'public, max-age=86400, s-maxage=86400');
     res.end(css);
 }
 
 function fetchBaseCss(res) {
-    fs.readFile('private/base.css', { encoding: 'utf8' }, (err, data) => respond(res, data));
+    let fname = `${__dirname}/../private/base.css`;
+    fs.readFile(fname, { encoding: 'utf8' }, (err, data) => respond(res, data));
 }
 
 function fetchMobileSiteCss(app, req, res) {
     return mwapi.getSiteInfo(app, req)
     .then(si => load(SITE_MODULES, req.params.domain, si.general.lang)
     .then(css => respond(res, css.body)));
 }
 
 function fetchPageLibCss(res) {
     fs.readFile(pageLibCss, { encoding: 'utf8' }, (err, data) => respond(res, data));
 }
 
 module.exports = {
     fetchBaseCss,
     fetchMobileSiteCss,
     fetchPageLibCss,
     respond,
     testing: {
         load,
         SITE_MODULES
     }
 };