diff --git a/lib/css-plugin.js b/lib/css-plugin.js
index b97bc1f9..43e040b3 100644
--- a/lib/css-plugin.js
+++ b/lib/css-plugin.js
@@ -90,7 +90,7 @@ export default function (resolveFileUrl) {
             }),
             postCSSUrl({
               url: ({ relativePath, url }) => {
-                if (/^(https?|data):/.test(url)) return url;
+                if (/^((https?|data):|#)/.test(url)) return url;
                 const parsedPath = parsePath(relativePath);
                 const source = readFileSync(
                   resolvePath(dirname(path), relativePath),