diff -u -r1.1.2.2 node_example/node_example.module
--- node_example.module	22 Oct 2009 14:29:35 -0000	1.1.2.2
+++ node_example.module	15 Dec 2009 00:52:25 -0000
@@ -163,16 +163,12 @@
  *
  * Errors should be signaled with form_set_error().
  */
-function node_example_validate(&$node) {
+function node_example_validate($node) {
   if ($node->quantity) {
     if (!is_numeric($node->quantity)) {
       form_set_error('quantity', t('The quantity must be a number.'));
     }
   }
-  else {
-    // Let an empty field mean "zero."
-    $node->quantity = 0;
-  }
 }
 
 /**