diff --git a/documentation/content/en/books/fdp-primer/examples/_index.adoc b/documentation/content/en/books/fdp-primer/examples/_index.adoc
--- a/documentation/content/en/books/fdp-primer/examples/_index.adoc
+++ b/documentation/content/en/books/fdp-primer/examples/_index.adoc
@@ -154,7 +154,7 @@
 
 This is the first section in my article.
 
-== My First Sub-Section
+=== My First Sub-Section
 
 This is the first sub-section in my article.