diff --git modules/system/system.base.css modules/system/system.base.css
index 65924bc..247b5d1 100644
--- modules/system/system.base.css
+++ modules/system/system.base.css
@@ -138,6 +138,7 @@ div.tree-child-horizontal {
 table.sticky-header {
   background-color: #fff;
   margin-top: 0;
+  z-index: 1;
 }
 
 /**