diff --git a/core/modules/field_ui/src/Form/FieldStorageConfigEditForm.php b/core/modules/field_ui/src/Form/FieldStorageConfigEditForm.php
index 40dbb73..0023a9d 100644
--- a/core/modules/field_ui/src/Form/FieldStorageConfigEditForm.php
+++ b/core/modules/field_ui/src/Form/FieldStorageConfigEditForm.php
@@ -52,13 +52,6 @@ public function buildForm(array $form, FormStateInterface $form_state, $field_co
       $form_state->set('bundle', $field->getTargetBundle());
     }
 
-    // Forbid access to the form if the field is locked.
-    if ($field->isLocked()) {
-      $form['locked'] = array(
-        '#markup' => $this->t('The field %field is locked and cannot be edited.', array('%field' => $field_config->getLabel())),
-      );
-    }
-
     return parent::buildForm($form, $form_state);
   }
 
@@ -69,6 +62,17 @@ public function form(array $form, FormStateInterface $form_state) {
     $form = parent::form($form, $form_state);
 
     $field_label = $form_state->get('field_config')->label();
+
+    // Forbid access to the form if the field is locked.
+    $field_storage = $form_state->get('field_config')->getFieldStorageDefinition();
+    if ($field_storage->isLocked()) {
+      $form['locked'] = array(
+        '#markup' => $this->t('The field %field is locked and cannot be edited.', array('%field' => $field_label)),
+      );
+
+      return $form;
+    }
+
     $form['#title'] = $field_label;
     $form['#prefix'] = '<p>' . $this->t('These settings apply to the %field field everywhere it is used. These settings impact the way that data is stored in the database and cannot be changed once data has been created.', array('%field' => $field_label)) . '</p>';