--- a/toolkit/themes/osx/global/nativescrollbars.css
+++ b/toolkit/themes/osx/global/nativescrollbars.css
@@ -8,33 +8,33 @@
 scrollbar {
   -moz-appearance: scrollbar;
   -moz-binding: url(chrome://global/content/bindings/scrollbar.xml#scrollbar);
   cursor: default;
   background-color: white;
   pointer-events: auto;
 }
 
-scrollbar[root="true"] {
-  position: relative;
-  z-index: 2147483647; /* largest positive value of a signed 32-bit integer */
+@media all and (-moz-overlay-scrollbars) {
+  scrollbar[root="true"] {
+    position: relative;
+    z-index: 2147483647; /* largest positive value of a signed 32-bit integer */
+  }
+
+  scrollbar:not([active="true"]),
+  scrollbar[disabled="true"] {
+    visibility: hidden;
+  }
 }
 
 html|select[size]:not([size="0"]):not([size="1"]) > scrollbar,
 html|select[multiple] > scrollbar {
   -moz-appearance: scrollbar-small;
 }
 
-@media all and (-moz-overlay-scrollbars) {
-  scrollbar:not([active="true"]),
-  scrollbar[disabled="true"] {
-    visibility: hidden;
-  }
-}
-
 /* ..... track ..... */
 
 slider {
   -moz-appearance: scrollbartrack-horizontal;
 }
 
 slider[orient="vertical"] {
   -moz-appearance: scrollbartrack-vertical;

--- a/toolkit/themes/windows/global/xulscrollbars.css
+++ b/toolkit/themes/windows/global/xulscrollbars.css
@@ -14,33 +14,33 @@
 scrollbar {
   -moz-appearance: scrollbartrack-horizontal;
   -moz-binding: url("chrome://global/content/bindings/scrollbar.xml#scrollbar");
   cursor: default;
   background: url("chrome://global/skin/scrollbar/slider.gif") scrollbar;
   pointer-events: auto;
 }
 
-scrollbar[root="true"] {
-  position: relative;
-  z-index: 2147483647; /* largest positive value of a signed 32-bit integer */
+@media all and (-moz-overlay-scrollbars) {
+  scrollbar[root="true"] {
+    position: relative;
+    z-index: 2147483647; /* largest positive value of a signed 32-bit integer */
+  }
+
+  scrollbar:not([active="true"]),
+  scrollbar[disabled="true"] {
+    visibility: hidden;
+  }
 }
 
 scrollbar[orient="vertical"] 
 {
    -moz-appearance: scrollbartrack-vertical;
 }
 
-@media all and (-moz-overlay-scrollbars) {
-  scrollbar:not([active="true"]),
-  scrollbar[disabled="true"] {
-    visibility: hidden;
-  }
-}
-
 /* ::::: borders for thumb and buttons ::::: */
 
 thumb,
 scrollbarbutton {
   border: 2px solid;
   -moz-border-top-colors: ThreeDLightShadow ThreeDHighlight;
   -moz-border-right-colors: ThreeDDarkShadow ThreeDShadow;
   -moz-border-bottom-colors: ThreeDDarkShadow ThreeDShadow;