diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index 7c150e9..ead66ce 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -302,18 +302,24 @@ public function castValue($value) {
    * Unsets value in this config object.
    *
    * @param string $key
-   *   Name of the key whose value should be unset.
+   *   (optional) The name of the key whose value should be unset. If omitted,
+   *   the entire config object is emptied.
    *
    * @return Drupal\Core\Config\Config
    *   The configuration object.
    */
-  public function clear($key) {
-    $parts = explode('.', $key);
-    if (count($parts) == 1) {
-      unset($this->data[$key]);
+  public function clear($key = NULL) {
+    if (!isset($key)) {
+      $this->data = array();
     }
     else {
-      NestedArray::unsetValue($this->data, $parts);
+      $parts = explode('.', $key);
+      if (count($parts) == 1) {
+        unset($this->data[$key]);
+      }
+      else {
+        NestedArray::unsetValue($this->data, $parts);
+      }
     }
     $this->resetOverriddenData();
     return $this;
@@ -346,7 +352,6 @@ public function load() {
    *   The configuration object.
    */
   public function save() {
-    $this->sortByKey($this->data);
     $this->storage->write($this->name, $this->data);
     $this->isNew = FALSE;
     $this->notify('save');
@@ -370,26 +375,6 @@ public function rename($new_name) {
   }
 
   /**
-   * Sorts all keys in configuration data.
-   *
-   * Ensures that re-inserted keys appear in the same location as before, in
-   * order to ensure an identical order regardless of storage controller.
-   * A consistent order is important for any storage that allows any kind of
-   * diff operation.
-   *
-   * @param array $data
-   *   An associative array to sort recursively by key name.
-   */
-  public function sortByKey(array &$data) {
-    ksort($data);
-    foreach ($data as &$value) {
-      if (is_array($value)) {
-        $this->sortByKey($value);
-      }
-    }
-  }
-
-  /**
    * Deletes the configuration object.
    *
    * @return Drupal\Core\Config\Config
diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php b/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php
index e82eb7f..b007968 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php
@@ -274,6 +274,10 @@ public function save(EntityInterface $entity) {
     $this->preSave($entity);
     $this->invokeHook('presave', $entity);
 
+    // Clear out any possibly existing keys in an existing configuration object,
+    // so any potentially stale keys are removed.
+    $config->clear();
+
     // Configuration objects do not have a schema. Extract all key names from
     // class properties.
     $class_info = new \ReflectionClass($entity);
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
index 9eea495..e0bc6a9 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
@@ -93,7 +93,7 @@ function testCRUD() {
   }
 
   /**
-   * Tests Drupal\Core\Config\Config::sortByKey().
+   * Tests key injection order.
    */
   function testDataKeySort() {
     $config = config('config_test.keysort');
@@ -106,8 +106,6 @@ function testDataKeySort() {
 
     // Load the configuration data into a new object.
     $new_config = config('config_test.keysort');
-    // Clear the 'new' key that came first.
-    $new_config->clear('new');
     // Add a new 'new' key and save.
     $new_config->set('new', 'Value to be replaced');
     $new_config->save();
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
index 532979c..58cb605 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
@@ -85,6 +85,19 @@ function testCRUD() {
     $this->assertResponse(200);
     $this->assertNoText($label1);
     $this->assertText($label3);
+    $id = $edit['id'];
+
+    // Add an orphan key to the configuration entity's object.
+    $config = config('config_test.dynamic.' . $id);
+    $config->set('foo', 'bar')->save();
+
+    // Re-save the configuration entity.
+    $this->drupalPost('admin/structure/config_test/manage/' . $id, array(), 'Save');
+    $this->assertResponse(200);
+
+    // Verify that the orphan key was destroyed.
+    $config = config('config_test.dynamic.' . $id);
+    $this->assertNull($config->get('foo'));
   }
 
 }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
index 9316962..2266732 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
@@ -128,10 +128,10 @@ function testNew() {
     $staging->write($name, $original_name_data);
     $original_dynamic_data = array(
       'id' => 'new',
+      'uuid' => '30df59bd-7b03-4cf7-bb35-d42fc49f0651',
       'label' => 'New',
-      'langcode' => 'und',
       'style' => '',
-      'uuid' => '30df59bd-7b03-4cf7-bb35-d42fc49f0651',
+      'langcode' => 'und',
     );
     $staging->write($dynamic_name, $original_dynamic_data);
     $this->assertIdentical($staging->exists($name), TRUE, $name . ' found.');