diff --git a/src/browser/base/content/zen-styles/zen-browser-ui.css b/src/browser/base/content/zen-styles/zen-browser-ui.css
index 3e04e2b42..4152b9ab6 100644
--- a/src/browser/base/content/zen-styles/zen-browser-ui.css
+++ b/src/browser/base/content/zen-styles/zen-browser-ui.css
@@ -8,6 +8,7 @@
 #navigator-toolbox {
   /* see issue #426 */
   background: var(--zen-navigator-toolbox-background, transparent) !important;
+  --inactive-titlebar-opacity: 1;
 }
 
 #browser {