diff --git a/src/Plugin/Field/FieldType/DynamicEntityReferenceItem.php b/src/Plugin/Field/FieldType/DynamicEntityReferenceItem.php
index 5b9757b5e3e97a243b1ff0606fe21aea3a92aa74..bad4be389ddf79137460e8a1eacda91fbdd290f9 100644
--- a/src/Plugin/Field/FieldType/DynamicEntityReferenceItem.php
+++ b/src/Plugin/Field/FieldType/DynamicEntityReferenceItem.php
@@ -150,7 +150,7 @@ class DynamicEntityReferenceItem extends EntityReferenceItem {
    *
    * @see \Drupal\dynamic_entity_reference\Plugin\Field\FieldWidget\DynamicEntityReferenceOptionsTrait::massageFormValues()
    */
-  public function getSettableOptions(AccountInterface $account = NULL) {
+  public function getSettableOptions(?AccountInterface $account = NULL) {
     $field_definition = $this->getFieldDefinition();
     $entity_type_manager = \Drupal::entityTypeManager();
     $entity_type_bundles_info = \Drupal::service('entity_type.bundle.info');
diff --git a/src/SelectionPluginManager.php b/src/SelectionPluginManager.php
index 4f003342144e210e2c095b6d74d82f003c1577cb..37a667742aa0680ac863f8b12dca99dd3854be8e 100644
--- a/src/SelectionPluginManager.php
+++ b/src/SelectionPluginManager.php
@@ -17,7 +17,7 @@ class SelectionPluginManager extends CoreSelectionPluginManager {
   /**
    * {@inheritdoc}
    */
-  public function getSelectionHandler(FieldDefinitionInterface $field_definition, EntityInterface $entity = NULL, $target_type = NULL) {
+  public function getSelectionHandler(FieldDefinitionInterface $field_definition, ?EntityInterface $entity = NULL, $target_type = NULL) {
     if ($target_type === NULL) {
       return parent::getSelectionHandler($field_definition, $entity);
     }