diff --git a/sphinx/static/default.css b/sphinx/static/default.css
index 09e43e23e..1c8cd87fe 100644
--- a/sphinx/static/default.css
+++ b/sphinx/static/default.css
@@ -702,6 +702,7 @@ pre {
     border: 1px solid #ac9;
     border-left: none;
     border-right: none;
+    overflow: auto;
 }
 
 td.linenos pre {