diff -u b/core/includes/install.inc b/core/includes/install.inc
--- b/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -414,8 +414,7 @@
   }
   config('system.module')
     ->set('system', 0)
-    ->setSorter('module_config_sort')
-    ->save();
+    ->save('module_config_sort');
 
   // Clear out module list and hook implementation statics before calling
   // system_rebuild_theme_data().
diff -u b/core/includes/module.inc b/core/includes/module.inc
--- b/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -467,8 +467,7 @@
     if (!$enabled) {
       $config
         ->set($module, $weight)
-        ->setSorter('module_config_sort')
-        ->save();
+        ->save('module_config_sort');
       if ($weight) {
         $weight_store->delete($module_list);
       }
@@ -592,8 +591,7 @@
       }
       $config
         ->clear($module)
-        ->setSorter('module_config_sort')
-        ->save();
+        ->save('module_config_sort');
       $invoke_modules[] = $module;
       watchdog('system', '%module module disabled.', array('%module' => $module), WATCHDOG_INFO);
     }
@@ -1153,8 +1151,7 @@
   if ($config->get($module) !== NULL) {
     $config
       ->set($module, $weight)
-      ->setSorter('module_config_sort')
-      ->save();
+      ->save('module_config_sort');
   }
   else {
     KeyValueFactory::get('system.module.weight')->set($module, $weight);
diff -u b/core/includes/update.inc b/core/includes/update.inc
--- b/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -38,9 +38,11 @@
     }
     if ($save) {
       if ($type == 'module') {
-        $config->setSorter('module_config_sort');
+        $config->save('module_config_sort');
+      }
+      else {
+        $config->save();
       }
-      $config->save();
     }
   }
 }
@@ -201,10 +203,8 @@
           }
         }
       }
-      $configs['module']->setSorter('module_config_sort');
-      foreach ($configs as $config) {
-        $config->save();
-      }
+      $configs['module']->save('module_config_sort');
+      $configs['theme']->save();
 
       // Update the dynamic include paths that might be used before running the
       // proper update functions.
@@ -406,8 +406,7 @@
     // Enable the module with a weight of 0.
     config('system.module')
       ->set($module, 0)
-      ->setSorter('module_config_sort')
-      ->save();
+      ->save('module_config_sort');
     // Change the schema version from SCHEMA_UNINSTALLED to 0, so any module
     // updates since the module's inception are executed in a core upgrade.
     $store->set($module, 0);
diff -u b/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
--- b/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -65,20 +65,6 @@
   protected $eventDispatcher;
 
   /**
-   * TRUE if the configuration object does not need sorting on save.
-   *
-   * @var bool
-   */
-  protected $sorted = FALSE;
-
-  /**
-   * The callable that sorts the data before save.
-   *
-   * @var callable
-   */
-  protected $sorter;
-
-  /**
    * Constructs a configuration object.
    *
    * @param string $name
@@ -323,20 +309,14 @@
   /**
    * Saves the configuration object.
    */
-  public function save() {
-    if (!$this->sorted) {
-      call_user_func($this->sorter ? $this->sorter : array($this, 'sortByKey'), $this->data);
-    }
+  public function save($sorter = FALSE) {
+    $this->data = call_user_func($sorter ? $sorter : array($this, 'sortByKey'), $this->data);
     $this->storage->write($this->name, $this->data);
     $this->isNew = FALSE;
     $this->notify('save');
     return $this;
   }
 
-  public function sorted() {
-    $this->sorted = TRUE;
-  }
-
   /*
    * Renames the configuration object.
    *
@@ -351,14 +331,6 @@
   }
 
   /**
-   * @param callable
-   */
-  function setSorter($sorter) {
-    $this->sorter = $sorter;
-    return $this;
-  }
-
-  /**
    * Sorts all keys in configuration data.
    *
    * Ensures that re-inserted keys appear in the same location as before, in