diff --git a/lisp/ox-html.el b/lisp/ox-html.el
index e835320b4..12e9e6a35 100644
--- a/lisp/ox-html.el
+++ b/lisp/ox-html.el
@@ -323,7 +323,7 @@ This affects IDs that are determined from the ID property.")
   pre.src-awk:before { content: 'Awk'; }
   pre.src-authinfo::before { content: 'Authinfo'; }
   pre.src-C:before { content: 'C'; }
-  /* pre.src-C++ doesn't work in CSS */
+  pre.src-C\\+\\+:before { content: 'C++'; }
   pre.src-clojure:before { content: 'Clojure'; }
   pre.src-css:before { content: 'CSS'; }
   pre.src-D:before { content: 'D'; }