diff --git a/doc/xsl/arm-param.xsl b/doc/xsl/arm-param.xsl
index 18af35c009..bd895fe335 100644
--- a/doc/xsl/arm-param.xsl
+++ b/doc/xsl/arm-param.xsl
@@ -38,8 +38,8 @@
   <xsl:template match="abstract"/>
   <xsl:template match="sidebar"/>
 
-  <!-- Two section level in the Table of contents -->
-  <xsl:param name="toc.section.depth">2</xsl:param>
+  <!-- Three section levels deep in the Table of contents -->
+  <xsl:param name="toc.section.depth">3</xsl:param>
 
   <!-- Do not show the collaborators listed in bookinfo -->
   <xsl:param name="doc.collab.show" select="0"/>