diff --git a/packages/tree-extension/style/base.css b/packages/tree-extension/style/base.css
index 0b2f62043..a22925be4 100644
--- a/packages/tree-extension/style/base.css
+++ b/packages/tree-extension/style/base.css
@@ -9,6 +9,12 @@
 .jp-TreePanel .lm-TabPanel-tabBar {
   overflow: visible;
   min-height: 32px;
+  border-bottom: unset;
+  height: var(--jp-private-toolbar-height);
+}
+
+.jp-TreePanel .lm-TabBar-content {
+  height: 100%;
 }
 
 .jp-TreePanel .lm-TabBar-tab {