diff --git a/layout/reftests/bugs/491323-1-ref.xul b/layout/reftests/bugs/491323-1-ref.xul
index 80c2331b032..bcfd636da22 100644
--- a/layout/reftests/bugs/491323-1-ref.xul
+++ b/layout/reftests/bugs/491323-1-ref.xul
@@ -2,6 +2,13 @@
 <window xmlns:html="http://www.w3.org/1999/xhtml"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 <hbox flex="1">
+  <html:style>
+    /* Make sure our splitter's background doesn't depend on its hover styles */
+    splitter {
+      background-color: yellow;
+      -moz-appearance: none;
+    }
+  </html:style>
   <splitter collapse="before" resizeafter="farthest" width="200" id="s">
   </splitter>
 </hbox>
diff --git a/layout/reftests/bugs/491323-1.xul b/layout/reftests/bugs/491323-1.xul
index 8245a0bb51a..e255d1d4d34 100644
--- a/layout/reftests/bugs/491323-1.xul
+++ b/layout/reftests/bugs/491323-1.xul
@@ -3,6 +3,13 @@
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
         onload="loaded()">
 <hbox flex="1">
+  <html:style>
+    /* Make sure our splitter's background doesn't depend on its hover styles */
+    splitter {
+      background-color: yellow;
+      -moz-appearance: none;
+    }
+  </html:style>
   <script>
   function loaded() {
     document.documentElement.getBoundingClientRect();