diff -u b/js/checkbox-widget.js b/js/checkbox-widget.js
--- b/js/checkbox-widget.js
+++ b/js/checkbox-widget.js
@@ -45,7 +45,7 @@
         // register handlers on that element.
         $widget.addClass('js-facets-widget');
 
-        facetSettings = drupalSettings.facets[$widget.data('drupal-facet-id')];
+        facetSettings = drupalSettings.facets[$widget.data('drupal-facet-id')] ?? {};
         // Transform links to checkboxes.
         $widgetLinks.each(Drupal.facets.makeCheckbox);
 
@@ -122,7 +122,7 @@
     var href = $link.attr('href');
     var id = $link.data('drupal-facet-item-id');
     var $widget = $(this).closest('.js-facets-widget');
-    var facetSettings = drupalSettings.facets[$widget.data('drupal-facet-id')];
+    var facetSettings = drupalSettings.facets[$widget.data('drupal-facet-id')] ?? {};
 
     var checkbox = $('<input type="checkbox" class="facets-checkbox">')
       .attr('id', id)
@@ -132,7 +132,8 @@
 
     // Do not trigger facets on change when auto-submit is disabled, so we can trigger them manually clicking on the
     // apply button.
-    if (!facetSettings.disable_autosubmit) {
+    var disableAutosubmit = facetSettings.disable_autosubmit ?? false;
+    if (!disableAutosubmit) {
       checkbox.on('change.facets', function (e) {
         e.preventDefault();