diff --git a/expat/doc/reference.html b/expat/doc/reference.html
index bd205ed4..c600fbba 100644
--- a/expat/doc/reference.html
+++ b/expat/doc/reference.html
@@ -1135,7 +1135,9 @@ containing part (or perhaps all) of the document. The number of bytes of s
 that are part of the document is indicated by <code>len</code>. This means
 that <code>s</code> doesn't have to be null-terminated. It also means that
 if <code>len</code> is larger than the number of bytes in the block of
-memory that <code>s</code> points at, then a memory fault is likely. The
+memory that <code>s</code> points at, then a memory fault is likely.
+Negative values for <code>len</code> are rejected since Expat 2.2.1.
+The
 <code>isFinal</code> parameter informs the parser that this is the last
 piece of the document. Frequently, the last piece is empty (i.e.
 <code>len</code> is zero.)
@@ -1183,11 +1185,17 @@ XML_ParseBuffer(XML_Parser p,
                 int isFinal);
 </pre>
 <div class="fcndef">
+<p>
 This is just like <code><a href= "#XML_Parse" >XML_Parse</a></code>,
 except in this case Expat provides the buffer.  By obtaining the
 buffer from Expat with the <code><a href= "#XML_GetBuffer"
 >XML_GetBuffer</a></code> function, the application can avoid double
 copying of the input.
+</p>
+
+<p>
+Negative values for <code>len</code> are rejected since Expat 2.6.3.
+</p>
 </div>
 
 <h4 id="XML_GetBuffer">XML_GetBuffer</h4>