diff -u b/simple_oauth.install b/simple_oauth.install
--- b/simple_oauth.install
+++ b/simple_oauth.install
@@ -5,10 +5,9 @@
  * Installation and updating routines.
  */
 
+use Drupal\Core\Config\FileStorage;
 use Drupal\Core\Field\BaseFieldDefinition;
-use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\Core\StringTranslation\TranslatableMarkup;
-use Drupal\Core\Entity\EntityDefinitionUpdateManagerInterface;
 
 /**
  * Define the default batch size.
@@ -54,59 +53,59 @@
 function simple_oauth_update_8404() {
   $use_implicit = \Drupal::config('simple_oauth_extras.settings')->get('use_implicit');
-  if ($use_implicit !== NULL) {
-    \Drupal::configFactory()
-      ->getEditable('simple_oauth.settings')
-      ->set('use_implicit', $use_implicit)
-      ->save();
+  if ($use_implicit === NULL) {
+    $config_path = drupal_get_path('module', 'simple_oauth') . '/config/install';
+    // Because of custom config_path, we don't call service here.
+    $source = new FileStorage($config_path);
+    $config_default = $source->read('simple_oauth.settings');
+    $use_implicit = $config_default['use_implicit'];
+  }
+  else {
     \Drupal::configFactory()
       ->getEditable('simple_oauth_extras.settings')
       ->delete();
   }
+  \Drupal::configFactory()
+    ->getEditable('simple_oauth.settings')
+    ->set('use_implicit', $use_implicit)
+    ->save();
   $query = \Drupal::database()->delete('key_value')
     ->condition('collection', 'system.schema')
     ->condition('name', 'simple_oauth_extras')
     ->execute();
   $field_names = ['redirect', 'user_id'];
-  $fields_installed = [];
   $entity_definition_update_manager = \Drupal::entityDefinitionUpdateManager();
-//  $changes = $entity_definition_update_manager->getChangeList()['consumer'];
-  $field_definitions = [
-    'redirect' => BaseFieldDefinition::create('uri')
-      ->setLabel(new TranslatableMarkup('Redirect URI'))
-      ->setDescription(new TranslatableMarkup('The URI this client will redirect to when needed.'))
-      ->setTranslatable(TRUE)
-      // URIs are not length limited by RFC 2616, but we can only store 255
-      // characters in our entity DB schema.
-      ->setSetting('max_length', 255)
-      ->setProvider('simple_oauth'),
-
-    'user_id' => BaseFieldDefinition::create('entity_reference')
-      ->setLabel(new TranslatableMarkup('User'))
-      ->setDescription(new TranslatableMarkup('When no specific user is authenticated Drupal will use this user as the author of all the actions made.'))
-      ->setRevisionable(TRUE)
-      ->setTranslatable(FALSE)
-      ->setCardinality(1)
-      ->setProvider('simple_oauth'),
-  ];
-  // If simple_oauth_extras wasn't installed, definitions should be missing.
+
   if ($query) {
+    // If simple_oauth_extras was installed, we need at least to update field
+    // provider.
     foreach ($field_names as $field_name) {
     $field_definition = $entity_definition_update_manager->getFieldStorageDefinition($field_name, 'consumer');
     $field_definition->setProvider('simple_oauth');
     $entity_definition_update_manager->updateFieldStorageDefinition($field_definition);
     }
-
   }
   else {
+    // If simple_oauth_extras wasn't installed, definitions should be missing.
+    $field_definitions = [
+      'redirect' => BaseFieldDefinition::create('uri')
+        ->setLabel(new TranslatableMarkup('Redirect URI'))
+        ->setDescription(new TranslatableMarkup('The URI this client will redirect to when needed.'))
+        ->setTranslatable(TRUE)
+        // URIs are not length limited by RFC 2616, but we can only store 255
+        // characters in our entity DB schema.
+        ->setSetting('max_length', 255)
+        ->setProvider('simple_oauth'),
+
+      'user_id' => BaseFieldDefinition::create('entity_reference')
+        ->setLabel(new TranslatableMarkup('User'))
+        ->setDescription(new TranslatableMarkup('When no specific user is authenticated Drupal will use this user as the author of all the actions made.'))
+        ->setRevisionable(TRUE)
+        ->setTranslatable(FALSE)
+        ->setCardinality(1)
+        ->setProvider('simple_oauth'),
+    ];
     foreach ($field_names as $field_name) {
-    //  if ($changes['field_storage_definitions'][$field_name] === EntityDefinitionUpdateManagerInterface::DEFINITION_CREATED) {
-    $entity_definition_update_manager->installFieldStorageDefinition($field_name, 'consumer', 'simple_oauth', $field_definitions[$field_name]);
-    $fields_installed []= $field_name;
-    //  }
+      $entity_definition_update_manager->installFieldStorageDefinition($field_name, 'consumer', 'simple_oauth', $field_definitions[$field_name]);
     }
-    // If simple_oauth_extras was installed, we need at least to update field
-    // provider.
-    //$field_names = array_diff($field_names, $fields_installed);
-
   }
 }