diff --git a/doc/smart_ptr.adoc b/doc/smart_ptr.adoc
index 8933811..2285134 100644
--- a/doc/smart_ptr.adoc
+++ b/doc/smart_ptr.adoc
@@ -14,6 +14,8 @@ Greg Colvin, Beman Dawes, Peter Dimov, Glen Fernandes
 :idprefix:
 :listing-caption: Code Example
 :docinfo: private-footer
+:source-highlighter: rouge
+:source-language: c++
 
 :leveloffset: +1