diff --git a/_static/custom.css b/_static/custom.css
index 639d5dc..935f95c 100644
--- a/_static/custom.css
+++ b/_static/custom.css
@@ -8,6 +8,6 @@ div.navbar-brand-box a.navbar-brand img {
 }
 
 .cell_output .output.stderr pre {
-  background-color: none;
+  background-color: transparent;
   color: #b3a783;
 }