diff --git a/mozilla/layout/html/document/src/quirk.css b/mozilla/layout/html/document/src/quirk.css
index a7db7f5e751..e7fdd10c0cd 100644
--- a/mozilla/layout/html/document/src/quirk.css
+++ b/mozilla/layout/html/document/src/quirk.css
@@ -275,6 +275,7 @@ hr {
   display: inline;
   -moz-box-sizing: border-box;
   margin: 0 0.1% 0 0.1%; /* Mmm! Hack-on-a-hack for bug 81776 */
+  font-size: -moz-initial !important;
 }
 
 hr:before {
diff --git a/mozilla/layout/style/quirk.css b/mozilla/layout/style/quirk.css
index a7db7f5e751..e7fdd10c0cd 100644
--- a/mozilla/layout/style/quirk.css
+++ b/mozilla/layout/style/quirk.css
@@ -275,6 +275,7 @@ hr {
   display: inline;
   -moz-box-sizing: border-box;
   margin: 0 0.1% 0 0.1%; /* Mmm! Hack-on-a-hack for bug 81776 */
+  font-size: -moz-initial !important;
 }
 
 hr:before {