diff --git a/reference/outcontrol/reference.xml b/reference/outcontrol/reference.xml
index d8b525f8f0..0838a95e68 100644
--- a/reference/outcontrol/reference.xml
+++ b/reference/outcontrol/reference.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.5 $ -->
+<!-- $Revision: 1.6 $ -->
  <reference id="ref.outcontrol">
   <title>Output Control Functions</title>
   <titleabbrev>Output Control</titleabbrev>
@@ -70,6 +70,15 @@ ob_end_flush();
      cookie without causing an error. (You can not normally send
      headers to the browser after data has already been sent.)
     </para>
+    <note>
+     <para>
+      When upgrading from PHP 4.1 (& 4.2) to 4.3 that due to a bug in
+      earlier versions you must ensure that
+      <literal>implict_flush</literal> is <literal>OFF</literal> in
+      your <literal>php.ini</literal>, otherwise any output with
+      <function>ob_start</function> will be not be hidden from output.
+     </para>
+    </note>
    </section>
 
    <section id="outcontrol.seealso">