diff --git a/aio/src/styles/1-layouts/_sidenav.scss b/aio/src/styles/1-layouts/_sidenav.scss
index 2e8b8c7baf..437a1abf2a 100644
--- a/aio/src/styles/1-layouts/_sidenav.scss
+++ b/aio/src/styles/1-layouts/_sidenav.scss
@@ -115,6 +115,7 @@ button.vertical-menu-item {
 }
 
 .heading-children.collapsed {
+  overflow: hidden;  // Needed to prevent unnecessary sidenav scrollbar.
   visibility: hidden;
   opacity: 0;
   max-height: 1px; // Must have measurement to transition height.