diff --git a/src/css/custom.css b/src/css/custom.css
index 939e1bc..cf64c09 100644
--- a/src/css/custom.css
+++ b/src/css/custom.css
@@ -28,3 +28,7 @@
   --ifm-color-primary-lightest: #4fddbf;
   --docusaurus-highlighted-code-line-bg: rgba(0, 0, 0, 0.3);
 }
+
+.theme-doc-sidebar-item-category-level-1 .menu__list-item {
+  border-left: 1px solid #ccc !important;
+}