diff --git a/language/constants.xml b/language/constants.xml
index b1c0ef34a5..f553407033 100644
--- a/language/constants.xml
+++ b/language/constants.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.42 $ -->
+<!-- $Revision: 1.43 $ -->
  <chapter id="language.constants">
   <title>Constants</title>
 
@@ -68,6 +68,7 @@ define("__FOO__", "something");
     Only scalar data (<type>boolean</type>, <type>integer</type>, 
     <type>float</type> and <type>string</type>) can be contained 
     in constants.
+    Do not define <type>resource</type> constants.
    </simpara>
    <simpara>
     You can get the value of a constant by simply specifying its name.