diff --git a/framework/core/less/forum/DiscussionPage.less b/framework/core/less/forum/DiscussionPage.less
index a1821ba69f..8166301e82 100644
--- a/framework/core/less/forum/DiscussionPage.less
+++ b/framework/core/less/forum/DiscussionPage.less
@@ -28,6 +28,7 @@
     position: sticky;
     top: var(--header-height);
     padding-top: 32px;
+    z-index: 1;
 
     &, > ul {
       width: 150px;