diff --git a/docs/manual/mod/mod_expires.html.en b/docs/manual/mod/mod_expires.html.en
index b1bca4fc76..40523ec084 100644
--- a/docs/manual/mod/mod_expires.html.en
+++ b/docs/manual/mod/mod_expires.html.en
@@ -52,6 +52,10 @@ criteria</td></tr>
     <code>max-age</code> (see <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9">RFC
     2616 section 14.9</a>), you can use the <code class="directive"><a href="../mod/mod_headers.html#header">Header</a></code> directive.</p>
 
+    <p> When the <code>Expires</code> header is already part of the response
+    generated by the server, for example when generated by a CGI script or 
+    proxied from an origin server, this module does not change or add
+    an <code>Expires</code> or <code>Cache-Control</code> header..</p>
 </div>
 <div id="quickview"><h3 class="directives">Directives</h3>
 <ul id="toc">
diff --git a/docs/manual/mod/mod_expires.xml b/docs/manual/mod/mod_expires.xml
index 067cb82238..bc646586ba 100644
--- a/docs/manual/mod/mod_expires.xml
+++ b/docs/manual/mod/mod_expires.xml
@@ -51,6 +51,10 @@ criteria</description>
     2616 section 14.9</a>), you can use the <directive
     module="mod_headers">Header</directive> directive.</p>
 
+    <p> When the <code>Expires</code> header is already part of the response
+    generated by the server, for example when generated by a CGI script or 
+    proxied from an origin server, this module does not change or add
+    an <code>Expires</code> or <code>Cache-Control</code> header..</p>
 </summary>
 
 <section id="AltSyn"><title>Alternate Interval Syntax</title>