diff --git a/src/js/redirect-engine.js b/src/js/redirect-engine.js
index ef3305559..e18ee7521 100644
--- a/src/js/redirect-engine.js
+++ b/src/js/redirect-engine.js
@@ -33,6 +33,7 @@ import {
 /******************************************************************************/
 
 const extToMimeMap = new Map([
+    [  'css', 'text/css' ],
     [  'gif', 'image/gif' ],
     [ 'html', 'text/html' ],
     [   'js', 'text/javascript' ],
diff --git a/src/web_accessible_resources/noop.css b/src/web_accessible_resources/noop.css
new file mode 100644
index 000000000..79a9626b5
--- /dev/null
+++ b/src/web_accessible_resources/noop.css
@@ -0,0 +1 @@
+/* */