diff --git a/modules/json_form_widget/src/WidgetRouter.php b/modules/json_form_widget/src/WidgetRouter.php
index e46ea481c3..25e3733c1a 100644
--- a/modules/json_form_widget/src/WidgetRouter.php
+++ b/modules/json_form_widget/src/WidgetRouter.php
@@ -174,7 +174,9 @@ public function handleListElement($spec, array $element) {
    */
   public function getDropdownElement($element, $spec, $titleProperty = FALSE) {
     $element['#type'] = $this->getSelectType($spec);
-    $element['#options'] = $this->getDropdownOptions($spec->source, $titleProperty);
+    if (isset($spec->source)) {
+      $element['#options'] = $this->getDropdownOptions($spec->source, $titleProperty);
+    }
     if ($element['#type'] === 'select_or_other_select') {
       $element = $this->handleSelectOtherDefaultValue($element, $element['#options']);
       $element['#input_type'] = isset($spec->other_type) ? $spec->other_type : 'textfield';