diff --git a/language/types.xml b/language/types.xml
index 913eaa6cd9..1fb58b48ad 100644
--- a/language/types.xml
+++ b/language/types.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.66 $ -->
+<!-- $Revision: 1.67 $ -->
  <chapter id="language.types">
   <title>Types</title>
 
@@ -237,7 +237,7 @@ if ($show_separators) {
         </listitem>
         <listitem>
          <simpara>the special type <link linkend="language.types.null"
-            >NULL</link> 
+           >NULL</link> (including unset variables)
          </simpara>
         </listitem>
        </itemizedlist>