diff --git a/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaManager.php b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaManager.php
index b72f2f3..2db8285 100644
--- a/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaManager.php
+++ b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaManager.php
@@ -238,7 +238,7 @@ public function applyChanges($entity_type_id = NULL) {
                 break;
 
               case static::DEFINITION_DELETED:
-                $this->onFieldStorageDefinitionDelete($storage_definitions[$field_name]);
+                $this->onFieldStorageDefinitionDelete($original_storage_definitions[$field_name]);
                 break;
             }
           }
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index f3b65a2..1085297 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -5,20 +5,20 @@
  * Configuration system that lets administrators modify the workings of the site.
  */
 
+use Drupal\Core\Block\BlockPluginInterface;
 use Drupal\Core\Cache\Cache;
+use Drupal\Core\Entity\ContentEntityTypeInterface;
 use Drupal\Core\Extension\Extension;
 use Drupal\Core\Extension\ExtensionDiscovery;
-use Drupal\Core\Form\FormState;
 use Drupal\Core\Form\FormStateInterface;
-use Drupal\Core\Routing\RouteMatchInterface;
-use Drupal\Core\StringTranslation\TranslationWrapper;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Menu\MenuTreeParameters;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\StringTranslation\TranslationWrapper;
 use Drupal\Core\Url;
-use Drupal\Core\Block\BlockPluginInterface;
 use Drupal\user\UserInterface;
-use Symfony\Component\HttpFoundation\RedirectResponse;
 use GuzzleHttp\Exception\RequestException;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
  * New users will be set to the default time zone at registration.
@@ -1032,11 +1032,39 @@ function system_sort_themes($a, $b) {
  * Implements hook_system_info_alter().
  */
 function system_system_info_alter(&$info, Extension $file, $type) {
-  // Remove page-top and page-bottom from the blocks UI since they are reserved for
-  // modules to populate from outside the blocks system.
-  if ($type == 'theme') {
-    $info['regions_hidden'][] = 'page_top';
-    $info['regions_hidden'][] = 'page_bottom';
+  switch ($type) {
+    case 'theme':
+      // Remove page-top and page-bottom from the blocks UI since they are
+      // reserved for modules to populate from outside the blocks system.
+      $info['regions_hidden'][] = 'page_top';
+      $info['regions_hidden'][] = 'page_bottom';
+      break;
+
+    case 'module':
+      // @todo Unify this with field_system_info_alter() once purging is
+      //   supported for any field. See https://www.drupal.org/node/2282119.
+      $module_name = $file->getName();
+      if ($module_name != 'field') {
+        $entity_manager = \Drupal::entityManager();
+        foreach ($entity_manager->getDefinitions() as $entity_type_id => $entity_type) {
+          if ($entity_type instanceof ContentEntityTypeInterface && $entity_manager->getStorage($entity_type_id)->hasData()) {
+            try {
+              foreach ($entity_manager->getFieldStorageDefinitions($entity_type_id) as $definition) {
+                if ($definition->getProvider() == $module_name) {
+                  $info['required'] = TRUE;
+                  $info['explanation'] = t('Fields type(s) in use');
+                  break;
+                }
+              }
+            }
+            catch (\LogicException $e) {
+              // If the entity type does not support retrieving base fields we
+              // have nothing to do here.
+            }
+          }
+        }
+      }
+      break;
   }
 }