Index: uc_upsell.module
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/uc_upsell/uc_upsell.module,v
retrieving revision 1.7.4.3
diff -u -p -w -r1.7.4.3 uc_upsell.module
--- uc_upsell.module	15 Jun 2009 02:46:04 -0000	1.7.4.3
+++ uc_upsell.module	11 Jan 2010 09:40:45 -0000
@@ -152,8 +152,12 @@ function uc_upsell_form_alter($form_id, 
         '#id' => 'upsell',
         );
 
-      $form['#submit'] = array_merge(array('uc_upsell_form_submit' => array($form_id, &$form_values)),
-        $form['#submit']);
+      if ( isset( $form['#submit'] ) && is_array( $form['#submit'] ) ) {
+        $form['#submit'] = array_merge(array('uc_upsell_form_submit' => array($form_id, &$form_values)), $form['#submit']);
+      }
+      else {
+        $form['#submit'] = array( array('uc_upsell_form_submit' => array($form_id, &$form_values)) ) ;
+      }
 
       $form['base']['relatedProducts'] = $assoc_form;
     }