diff --git a/functions/filesystem.xml b/functions/filesystem.xml
index 33edb38390..be4ae973b6 100644
--- a/functions/filesystem.xml
+++ b/functions/filesystem.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.108 $ -->
+<!-- $Revision: 1.109 $ -->
  <reference id="ref.filesystem">
   <title>Filesystem functions</title>
   <titleabbrev>Filesystem</titleabbrev>
@@ -1726,6 +1726,10 @@ luigi   florist it
      of <parameter>string</parameter> is reached, whichever comes
      first.
     </simpara>
+    <simpara>
+     <function>fwrite</function> returns the number of bytes
+     written, or -1 on error.
+    </simpara>
     <simpara>
      Note that if the <parameter>length</parameter> argument is given,
      then the <link