diff --git a/src/browser/base/content/zen-styles/zen-tabs/vertical-tabs.css b/src/browser/base/content/zen-styles/zen-tabs/vertical-tabs.css
index 4239a5113..1c97384a6 100644
--- a/src/browser/base/content/zen-styles/zen-tabs/vertical-tabs.css
+++ b/src/browser/base/content/zen-styles/zen-tabs/vertical-tabs.css
@@ -469,10 +469,9 @@
     #navigator-toolbox[has-popup-menu],
     #navigator-toolbox:has(.tabbrowser-tab:active),
     #navigator-toolbox:has(*[open='true']:not(tab):not(#zen-sidepanel-button)) {
-      --zen-navigation-toolbar-min-width: 55.5px !important; /* + the width of the splitter */
-
-      max-width: var(--zen-navigation-toolbar-min-width) !important;
-      min-width: var(--zen-navigation-toolbar-min-width) !important;
+      --zen-toolbox-max-width: 45px;
+      max-width: var(--zen-toolbox-max-width) !important;
+      min-width: calc(var(--zen-toolbox-max-width) + var(--zen-toolbox-padding) / 2 + 2px) !important;
       padding: 0 !important;
 
       & #TabsToolbar {