diff --git a/notebook/static/tree/less/tree.less b/notebook/static/tree/less/tree.less
index 38fc1a954d..1528d19662 100644
--- a/notebook/static/tree/less/tree.less
+++ b/notebook/static/tree/less/tree.less
@@ -33,6 +33,10 @@ ul#tabs a {
     padding-right: 0;
 }
 
+.btn-group {
+    z-index: 10;
+}
+
 ul.breadcrumb {
     a:focus, a:hover {
         text-decoration: none;