--- a/layout/style/html.css
+++ b/layout/style/html.css
@@ -756,8 +756,42 @@ marquee[direction="up"], marquee[directi
 }
 
 /* PRINT ONLY rules follow */
 @media print {
 
   marquee { -moz-binding: none; }
 
 }
+
+/* Ruby */
+
+@supports (display: ruby) {
+  ruby {
+    display: ruby;
+  }
+  rb {
+    display: ruby-base;
+    white-space: nowrap;
+  }
+  rp {
+    display: none;
+  }
+  rt {
+    display: ruby-text;
+    font-variant-east-asian: ruby;
+    text-emphasis: none;
+  }
+  rtc {
+    display: ruby-text-container;
+  }
+  rtc, rt {
+    white-space: nowrap;
+    font-size: 50%;
+    line-height: 1;
+  }
+  rtc > rt {
+    font-size: inherit;
+  }
+  ruby, rb, rt, rbc, rtc {
+    unicode-bidi: isolate;
+  }
+}

--- a/layout/style/ua.css
+++ b/layout/style/ua.css
@@ -68,17 +68,17 @@
 }
 
 *|*::-moz-table-cell {
   display: table-cell !important;
   white-space: inherit;
 }
 
 /* Ruby */
-@supports(display:ruby) {
+@supports (display:ruby) {
   *|*::-moz-ruby {
     display: ruby;
   }
   *|*::-moz-ruby-base {
     display: ruby-base;
   }
   *|*::-moz-ruby-text {
     display: ruby-text;