diff --git a/core/lib/Drupal/Core/Field/FieldItemList.php b/core/lib/Drupal/Core/Field/FieldItemList.php
index 4bfcbf9ef8..0b1960f229 100644
--- a/core/lib/Drupal/Core/Field/FieldItemList.php
+++ b/core/lib/Drupal/Core/Field/FieldItemList.php
@@ -262,7 +262,8 @@ public function generateSampleItems($count = 1) {
     $field_type_class = $field_definition->getItemDefinition()->getClass();
     $values = $this->getValue();
     for ($delta = 0; $delta < $count; $delta++) {
-      if ($value = $field_type_class::generateSampleValue($field_definition)) {
+      $value = $field_type_class::generateSampleValue($field_definition);
+      if (!is_null($value)) {
         $values[$delta] = $value;
       }
     }