diff --git a/frontend/src/components/TagDetailSidebar.test.tsx b/frontend/src/components/TagDetailSidebar.test.tsx
index e89683f..14bb255 100644
--- a/frontend/src/components/TagDetailSidebar.test.tsx
+++ b/frontend/src/components/TagDetailSidebar.test.tsx
@@ -39,6 +39,18 @@ describe ('TagDetailSidebar', () => {
     vi.clearAllMocks ()
   })
 
+  it ('inherits the sidebar width saved by the post list', () => {
+    localStorage.setItem ('sidebar:posts-index-tags:left:width', '320')
+
+    const { container } = renderWithProviders (
+	<TagDetailSidebar post={buildPost ()}/>)
+    const sidebar = container.querySelector<HTMLElement> (
+	'[style*="--sidebar-width"]')
+
+    expect (sidebar).toBeInTheDocument ()
+    expect (sidebar?.style.getPropertyValue ('--sidebar-width')).toBe ('320px')
+  })
+
   it ('keeps internal and external tags with the same numeric id in flat mode', () => {
     setClientTagRelationDisplayMode ('flat')