diff --git a/includes/webform2pdf.settings.inc b/includes/webform2pdf.settings.inc
index 92abbc2..038745e 100644
--- a/includes/webform2pdf.settings.inc
+++ b/includes/webform2pdf.settings.inc
@@ -624,8 +624,10 @@ function webform2pdf_edit_form($form, &$form_state, $node) {
   }
 
   if ( count($send_mail) ) {
-    $def = unserialize($default['no_send_email_addr']);
-    if ( !is_array($def) ) {
+    if (isset($default['no_send_email_addr'])) {
+      $def = unserialize($default['no_send_email_addr']);
+    }
+    if (!isset($def) || !is_array($def) ) {
       $def = array();
     }