diff --git a/src/bullet_threading.scss b/src/bullet_threading.scss
index 1664b3d..6385398 100644
--- a/src/bullet_threading.scss
+++ b/src/bullet_threading.scss
@@ -18,7 +18,7 @@
 }
 
 .block-children-left-border {
-  z-index: 10;
+  z-index: 1;
   position: absolute;
   height: 100%;
   width: 4px;