diff --git a/features/file-upload.xml b/features/file-upload.xml
index 112af0ed75..8b9254bd23 100644
--- a/features/file-upload.xml
+++ b/features/file-upload.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.63 $ -->
+<!-- $Revision: 1.64 $ -->
  <chapter id="features.file-upload">
   <title>Handling file uploads</title>
 
@@ -214,6 +214,11 @@ print "</pre>";
     Whatever the logic, you should either delete the file from the
     temporary directory or move it elsewhere.
    </simpara>
+   <simpara>
+    If no file is selected for upload in your form, PHP will return
+    $_FILES['userfile']['size'] as 0, and $_FILES['userfile']['tmp_name'] as
+    none.
+   </simpara>
    <simpara>
     The file will be deleted from the temporary directory at the end
     of the request if it has not been moved away or renamed.