diff --git a/book/source/16-policy.md b/book/source/15-policy.md
similarity index 100%
rename from book/source/16-policy.md
rename to book/source/15-policy.md
diff --git a/book/source/17-versions.md b/book/source/16-versions.md
similarity index 85%
rename from book/source/17-versions.md
rename to book/source/16-versions.md
index 1043db1..98db81e 100644
--- a/book/source/17-versions.md
+++ b/book/source/16-versions.md
@@ -4,7 +4,9 @@ SPDX-License-Identifier: CC-BY-SA-4.0
 -->
 
 (versions)=
-# Differences between OpenPGP versions
+# OpenPGP versions
+
+## Differences between OpenPGP versions
 
 ```{admonition} TODO
 :class: warning
diff --git a/book/source/15-migration.md b/book/source/17-migration.md
similarity index 100%
rename from book/source/15-migration.md
rename to book/source/17-migration.md