--- a/toolkit/themes/shared/in-content/info-pages.inc.css
+++ b/toolkit/themes/shared/in-content/info-pages.inc.css
@@ -35,17 +35,17 @@ body {
   background-position: left 0;
   background-repeat: no-repeat;
   background-size: 1.6em;
   margin-inline-start: -2.3em;
   padding-inline-start: 2.3em;
   font-size: 2.5em;
 }
 
-.title:dir(rtl) {
+.title:-moz-locale-dir(rtl) {
   background-position: right 0;
 }
 
 .title-text {
   border-bottom: 1px solid #C1C1C1;
   font-size: inherit;
   padding-bottom: 0.4em;
 }