diff --git a/doc/lambda2.adoc b/doc/lambda2.adoc
index 2ab0cba..29a6616 100644
--- a/doc/lambda2.adoc
+++ b/doc/lambda2.adoc
@@ -11,6 +11,8 @@ Peter Dimov
 :idprefix:
 :listing-caption: Code Example
 :docinfo: private-footer
+:source-highlighter: rouge
+:source-language: c++
 
 :leveloffset: +1