diff --git a/assets/theme-css/pst/base/_base.scss b/assets/theme-css/pst/base/_base.scss
index f48bc20b..7f29e5ef 100644
--- a/assets/theme-css/pst/base/_base.scss
+++ b/assets/theme-css/pst/base/_base.scss
@@ -168,7 +168,6 @@ pre {
 
 // the back to top btn
 #pst-back-to-top {
-  z-index: $zindex-tooltip;
   position: fixed;
   display: none;
   top: 90vh;