diff --git a/doc/kwantdoctheme/static/kwantdoctheme.css b/doc/kwantdoctheme/static/kwantdoctheme.css
index 8837f6ee74e9222e87c1edb10f5294864daa12d5..167ec2cab2c674a2eeeb2cbe0c454129273883db 100644
--- a/doc/kwantdoctheme/static/kwantdoctheme.css
+++ b/doc/kwantdoctheme/static/kwantdoctheme.css
@@ -94,6 +94,10 @@ div.body pre {
     border: 1px solid #ac9;
 }
 
+div.body pre.CodeMirror-line {
+    border: unset;
+}
+
 div.body div.admonition, div.body div.impl-detail {
     border-radius: 3px;
 }