diff --git a/lib/rdoc/generator/template/darkfish/css/rdoc.css b/lib/rdoc/generator/template/darkfish/css/rdoc.css
index 3d5b4b993e..1be815f503 100644
--- a/lib/rdoc/generator/template/darkfish/css/rdoc.css
+++ b/lib/rdoc/generator/template/darkfish/css/rdoc.css
@@ -505,7 +505,7 @@ main header h3 {
 
 main .method-source-code {
   max-height: 0;
-  overflow: hidden;
+  overflow: auto;
   transition-duration: 200ms;
   transition-delay: 0ms;
   transition-property: all;