--- a/browser/themes/windows/browser-aero.css
+++ b/browser/themes/windows/browser-aero.css
@@ -333,22 +333,23 @@
     background-color: rgba(255,255,255,.5);
     color: black;
     border-radius: 4px;
   }
 
   /* Artificially draw window borders that are covered by lwtheme, see bug 591930.
    * We use a different border for win8, and this is not necessary on win10+ */
   #main-window[sizemode="normal"] > #tab-view-deck > #browser-panel:-moz-lwtheme {
-    border-top: 2px solid;
-    -moz-border-top-colors: @glassActiveBorderColor@ rgba(255,255,255,.6);
+    border-top: 1px solid @glassActiveBorderColor@;
+    padding-top: 1px;
+    box-shadow: 0 1px 0 rgba(255,255,255,.6) inset;
   }
 
   #main-window[sizemode="normal"] > #tab-view-deck > #browser-panel:-moz-lwtheme:-moz-window-inactive {
-    -moz-border-top-colors: @glassInactiveBorderColor@ rgba(255,255,255,.6);
+    border-top-color: @glassInactiveBorderColor@;
   }
 }
 
 /* Aero Basic */
 @media (-moz-windows-compositor: 0) {
   @media (-moz-windows-default-theme) {
     #main-window {
       background-color: rgb(185,209,234);

--- a/browser/themes/windows/compacttheme.css
+++ b/browser/themes/windows/compacttheme.css
@@ -149,16 +149,18 @@
 
 /* Restored windows get an artificial border on windows, because the lwtheme background
  * overlaps the regular window border. That isn't the case for us, so we avoid painting
  * over the native border with our custom borders: */
 #browser-panel {
   /* These are !important to avoid specificity-wars with the selectors that add borders here. */
   background-image: none !important;
   border-top: none !important;
+  box-shadow: none !important;
+  padding-top: 0 !important;
 }
 
 @media (-moz-os-version: windows-win10) {
   .titlebar-button:-moz-lwtheme {
     -moz-context-properties: stroke;
     stroke: currentColor;
   }
   #titlebar-min:-moz-lwtheme {