diff --git a/asciidoc/pve-docbook.conf b/asciidoc/pve-docbook.conf
index 95436ec..e179342 100644
--- a/asciidoc/pve-docbook.conf
+++ b/asciidoc/pve-docbook.conf
@@ -5,6 +5,7 @@
 #
 # modified for Proxmox VE docs
 # - add thumbnail attribute
+# - render sect4 sections in manpages as formalpara title
 
 [miscellaneous]
 outfilesuffix=.xml
@@ -693,6 +694,16 @@ template::[docinfo]
 |
 </refsect3>
 
+# Proxmox: add custom section 4 level for manpages, as there is no refsect4 and
+# the XML DTD schema does not allows nesting refsect3 (even if it would render
+# OK). Use a formalpara, which is a paragraph with a title. As docbook always
+# outputs a simpara (simple paragraph, very limited) for the inner content, we
+# cannot nest that either, but rather just create an empty formalpara which can
+# then be followed by whatever the original inner content is.
+[sect4]
+<formalpara{id? id="{id}"}{role? role="{role}"}><title>{title}</title><para></para></formalpara>
+|
+
 endif::doctype-manpage[]
 
 #-------------------------