diff --git a/linkchecker.module b/linkchecker.module
index 311a0a0..9401aba 100644
--- a/linkchecker.module
+++ b/linkchecker.module
@@ -608,7 +608,11 @@ function linkchecker_block_custom_delete_form_submit($form, &$form_state) {
 function _linkchecker_add_node_links($node, $skip_missing_links_detection = FALSE) {
   // Get current node language options for url() functions.
   $languages = language_list();
-  $url_options = empty($node->language) ? array('absolute' => TRUE) : array('language' => $languages[$node->language], 'absolute' => TRUE);
+  $url_options = array('absolute' => TRUE);
+  // Note: Undefined language (value 'und') isn't listed in the available languages.
+  if (isset($node->language, $languages[$node->language])) {
+    $url_options = array('language' => $languages[$node->language], 'absolute' => TRUE);
+  }
 
   $filter = new stdClass;
   $filter->settings['filter_url_length'] = 72;
@@ -1039,8 +1043,9 @@ function linkchecker_parse_fields($bundle, $entity, $type) {
         case 'text_with_summary':
           foreach ($entity_field as $language) {
             foreach ($language as $item) {
-              $text_items[] = _linkchecker_check_markup($item['value'], $item['format'], $entity->language, TRUE);
-              $text_items[] = _linkchecker_check_markup($item['summary'], $item['format'], $entity->language, TRUE);
+              $format = isset($item['format']) ? $item['format'] : NULL;
+              $text_items[] = _linkchecker_check_markup($item['value'], $format, $entity->language, TRUE);
+              $text_items[] = _linkchecker_check_markup($item['summary'], $format, $entity->language, TRUE);
             }
           }
           break;
@@ -1050,7 +1055,8 @@ function linkchecker_parse_fields($bundle, $entity, $type) {
         case 'text':
           foreach ($entity_field as $language) {
             foreach ($language as $item) {
-              $text_items[] = _linkchecker_check_markup($item['value'], $item['format'], $entity->language, TRUE);
+              $format = isset($item['format']) ? $item['format'] : NULL;
+              $text_items[] = _linkchecker_check_markup($item['value'], $format, $entity->language, TRUE);
             }
           }
           break;