diff --git a/css/common-files/color_variables.css b/css/common-files/color_variables.css
index b65138a..d53e871 100644
--- a/css/common-files/color_variables.css
+++ b/css/common-files/color_variables.css
@@ -14,6 +14,7 @@
 @-moz-document url-prefix(https://discovery.addons.mozilla.org),
 url-prefix(chrome://),
 url-prefix(about:),
+url-prefix(file:),
 url(https://www.mozilla.org/credits/),
 url-prefix(https://addons.mozilla.org),
 url-prefix(http://addons.mozilla.org),
@@ -153,4 +154,4 @@ regexp(".*\\.(p|P)(d|D)(f|F).*") {
     --end-indicator-for-updater-scripts: black;
     --dummy-variable-for-updater-scripys: black
   }
-}
\ No newline at end of file
+}