--- a/browser/base/content/browser-tabsintitlebar.js
+++ b/browser/base/content/browser-tabsintitlebar.js
@@ -180,22 +180,20 @@ var TabsInTitlebar = {
 
       // And get the height of what's in the titlebar:
       let titlebarContentHeight = rect(titlebarContent).height;
 
       // Begin setting CSS properties which will cause a reflow
 
       // On Windows 10, adjust the window controls to span the entire
       // tab strip height if we're not showing a menu bar.
-      if (AppConstants.isPlatformAndVersionAtLeast("win", "10.0")) {
-        if (!menuHeight) {
-          // Add a pixel to slightly overlap the navbar border.
-          titlebarContentHeight = fullTabsHeight + 1;
-          $("titlebar-buttonbox").style.height = titlebarContentHeight + "px";
-        }
+      if (AppConstants.isPlatformAndVersionAtLeast("win", "10.0") &&
+          !menuHeight) {
+        titlebarContentHeight = fullTabsHeight;
+        $("titlebar-buttonbox").style.height = titlebarContentHeight + "px";
       }
 
       // If the menubar is around (menuHeight is non-zero), try to adjust
       // its full height (i.e. including margins) to match the titlebar,
       // by changing the menubar's bottom padding
       if (menuHeight) {
         // Calculate the difference between the titlebar's height and that of the menubar
         let menuTitlebarDelta = titlebarContentHeight - fullMenuHeight;