diff --git a/reference/iconv/ini.xml b/reference/iconv/ini.xml
index b27b4d12a3..3b60f1ebc0 100644
--- a/reference/iconv/ini.xml
+++ b/reference/iconv/ini.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.4 $ -->
+<!-- $Revision: 1.5 $ -->
 <section id="iconv.configuration">
  &reftitle.runtime;
  &extension.runtime;
@@ -39,6 +39,12 @@
  </table>
  &ini.php.constants;
  </para>
+ <warning>
+  <para>
+   Some systems (like IBM AIX) use "ISO8859-1" instead of "ISO-8859-1" so this
+   value has to be used in configuration options and function parameters.
+  </para>
+ </warning>
  <note>
   <para>
    Configuration option <parameter>iconv.input_encoding</parameter> is