diff --git a/doc/pickle.html b/doc/pickle.html
index 49f5c605..3ec8c928 100644
--- a/doc/pickle.html
+++ b/doc/pickle.html
@@ -38,7 +38,7 @@ described in detail in the
 >Python Library Reference for pickle.</a>
 
 <hr>
-<h1>The Boost.Python Pickle Interface</h1>
+<h2>The Boost.Python Pickle Interface</h2>
 
 At the user level, the Boost.Python pickle interface involves three special
 methods:
@@ -93,7 +93,7 @@ returned by __getstate__ need not be a dictionary. The __getstate__ and
 __setstate__ methods can do what they want.
 
 <hr>
-<h1>Pitfalls and Safety Guards</h1>
+<h2>Pitfalls and Safety Guards</h2>
 
 In Boost.Python extension modules with many extension classes, providing
 complete pickle support for all classes would be a significant
@@ -202,7 +202,7 @@ __getstate__ is defined and the instance's __dict__ is not empty.
 </dl>
 
 <hr>
-<h1>Practical Advice</h1>
+<h2>Practical Advice</h2>
 
 <ul>
 <li>