--- uc_cart.module      2009-08-20 13:09:21.000000000 +0100
+++ uc_cart.module-imac20090820 2009-08-20 13:14:26.000000000 +0100
@@ -289,7 +289,7 @@ function uc_cart_exit() {
  * Implementation of hook_nodeapi().
  */
 function uc_cart_nodeapi(&$node, $op, $arg3, $arg4) {
-  if (uc_product_is_product($node->type)) {
+  if ((function_exists('uc_product_is_product')) && (uc_product_is_product($node->type))) {
     switch ($op) {
       case 'delete':
         db_query("DELETE FROM {uc_cart_products} WHERE nid = %d", $node->nid);