diff --git a/src/Plugin/Block/FieldBlock.php b/src/Plugin/Block/FieldBlock.php
index a225157aa57a63f3e8222588f4d57ad9bb0d1492..ae95368c7e9e3f9ffc885816ed2417299c6cce20 100644
--- a/src/Plugin/Block/FieldBlock.php
+++ b/src/Plugin/Block/FieldBlock.php
@@ -18,6 +18,7 @@ use Drupal\Core\Field\FormatterInterface;
 use Drupal\Core\Field\FormatterPluginManager;
 use Drupal\Core\Form\FormHelper;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Form\SubformStateInterface;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\Core\Session\AccountInterface;
@@ -155,6 +156,16 @@ class FieldBlock extends BlockBase implements ContainerFactoryPluginInterface {
    * {@inheritdoc}
    */
   public function blockForm($form, FormStateInterface $form_state) {
+    // This method receives a sub form state instead of the full form state.
+    // There is an ongoing discussion around this which could result in the
+    // passed form state going back to a full form state. In order to prevent
+    // future breakage because of a core update we'll just check which type of
+    // FormStateInterface we've been passed and act accordingly.
+    // @See https://www.drupal.org/node/2798261
+    if ($form_state instanceof SubformStateInterface) {
+      $form_state = $form_state->getCompleteFormState();
+    }
+
     $form['label_from_field'] = [
       '#title' => $this->t('Use field label as block title'),
       '#type' => 'checkbox',