--- a/browser/themes/linux/browser.css
+++ b/browser/themes/linux/browser.css
@@ -656,47 +656,41 @@ notification[value="translation"] menuli
   }
 
   /* Add extra space to titlebar for dragging */
   :root[sizemode="normal"][chromehidden~="menubar"] #TabsToolbar,
   :root[sizemode="normal"] #toolbar-menubar[autohide="true"][inactive] + #TabsToolbar {
     padding-top: var(--space-above-tabbar);
   }
 
-  /**
-   * Titlebar items (window caption buttons, private browsing indicator,
-   * accessibility indicator, etc)
-   */
-  :root[sizemode="normal"][chromehidden~="menubar"] #TabsToolbar > .titlebar-item,
-  :root[sizemode="normal"] #toolbar-menubar[autohide="true"][inactive] + #TabsToolbar > .titlebar-item {
+  /* Center items (window caption buttons, private browsing indicator,
+   * accessibility indicator, etc) vertically. */
+  :root[sizemode="normal"] #TabsToolbar > .titlebar-item {
     margin-top: calc(-1 * var(--space-above-tabbar));
   }
 
   /* Make #TabsToolbar transparent as we style underlying #titlebar with
-   * -moz-window-titlebar (Gtk+ theme).
-   */
+   * -moz-window-titlebar (Gtk+ theme). */
   :root[tabsintitlebar][sizemode="normal"]:not([inFullscreen]) #TabsToolbar,
   :root[tabsintitlebar][sizemode="maximized"] #TabsToolbar,
   :root[tabsintitlebar] #toolbar-menubar {
     -moz-appearance: none;
   }
 
   /* The button box must appear on top of the navigator-toolbox in order for
    * click and hover mouse events to work properly for the button in the restored
    * window state. Otherwise, elements in the navigator-toolbox, like the menubar,
-   * can swallow those events.
-   */
+   * can swallow those events. */
   .titlebar-buttonbox {
     z-index: 1;
     -moz-box-align: center;
   }
 
   /* Render titlebar command buttons according to system config.
-   * Use full scale icons here as the Gtk+ does.
-   */
+   * Use full scale icons here as the Gtk+ does. */
   @media (-moz-gtk-csd-minimize-button) {
     .titlebar-min {
       -moz-appearance: -moz-window-button-minimize;
     }
   }
   @media (-moz-gtk-csd-minimize-button: 0) {
     .titlebar-min {
       display: none;

--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@@ -949,31 +949,31 @@ notification[value="translation"] {
  * paint, so this hack is how we sidestep that performance bottleneck.
  */
 #main-window:-moz-any([customize-entering],[customize-exiting]) label {
   transform: perspective(0.01px);
 }
 
 /* End customization mode */
 
-/**
- * Titlebar items (window caption buttons, private browsing indicator,
- * accessibility indicator, etc)
- */
-:root[sizemode="normal"][chromehidden~="menubar"] .titlebar-item,
-:root[sizemode="normal"] #toolbar-menubar[autohide="true"][inactive] + #TabsToolbar > .titlebar-item,
-:root[sizemode="normal"] #toolbar-menubar[autohide="true"][inactive] > .titlebar-item {
+/* Prevent titlebar items (window caption buttons, private browsing indicator,
+ * accessibility indicator, etc) from overlapping the nav bar's shadow on the
+ * tab bar. */
+#TabsToolbar > .titlebar-item {
+  margin-bottom: @navbarTabsShadowSize@;
+}
+
+/* Center titlebar items vertically. */
+:root[sizemode="normal"] #TabsToolbar > .titlebar-item {
   margin-top: calc(-1 * var(--space-above-tabbar));
 }
 
 /* Compensate for 4px extra margin on top of the tabs toolbar on Windows 7. */
 @media (-moz-os-version: windows-win7) {
-  :root[sizemode="normal"][chromehidden~="menubar"] .titlebar-item,
-  :root[sizemode="normal"] #toolbar-menubar[autohide="true"][inactive] + #TabsToolbar > .titlebar-item,
-  :root[sizemode="normal"] #toolbar-menubar[autohide="true"][inactive] > .titlebar-item {
+  :root[sizemode="normal"] #TabsToolbar > .titlebar-item {
     margin-top: calc(-1 * (var(--space-above-tabbar) + 4px));
   }
 }
 
 :root:not([privatebrowsingmode=temporary]) .accessibility-indicator,
 .private-browsing-indicator {
   margin-inline-end: 12px;
 }