diff --git a/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Category/index.tsx b/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Category/index.tsx
index 52c683c001f8..700c4a52bef3 100644
--- a/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Category/index.tsx
+++ b/packages/docusaurus-theme-classic/src/theme/DocSidebarItem/Category/index.tsx
@@ -136,7 +136,7 @@ export default function DocSidebarItemCategory({
   useEffect(() => {
     if (
       collapsible &&
-      expandedItem &&
+      expandedItem != null &&
       expandedItem !== index &&
       autoCollapseCategories
     ) {