diff --git a/layout/html/document/src/html.css b/layout/html/document/src/html.css
index 1750de3b195a..3eb7e5161a4d 100644
--- a/layout/html/document/src/html.css
+++ b/layout/html/document/src/html.css
@@ -362,7 +362,7 @@ dir ol dir,   dir ul dir,   dir menu dir,   dir dir dir {
 
 hr {
   display: block;
-  border: 1px -moz-bg-inset;
+  border: 1px inset;
   margin: 0 auto 0 auto;
 }
 
diff --git a/layout/style/html.css b/layout/style/html.css
index 1750de3b195a..3eb7e5161a4d 100644
--- a/layout/style/html.css
+++ b/layout/style/html.css
@@ -362,7 +362,7 @@ dir ol dir,   dir ul dir,   dir menu dir,   dir dir dir {
 
 hr {
   display: block;
-  border: 1px -moz-bg-inset;
+  border: 1px inset;
   margin: 0 auto 0 auto;
 }