diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php b/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php
index 458d765..824d18e 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Config\Entity;
 
+use Drupal\Component\Utility\String;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityMalformedException;
 use Drupal\Core\Entity\EntityStorageControllerBase;
@@ -14,6 +15,7 @@
 use Drupal\Core\Config\ConfigFactory;
 use Drupal\Core\Config\StorageInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Entity\EntityStorageException;
 use Drupal\Core\Entity\Query\QueryFactory;
 use Drupal\Component\Uuid\UuidInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -346,6 +348,12 @@ public function save(EntityInterface $entity) {
     $config = $this->configFactory->get($prefix . $id);
     $is_new = $config->isNew();
 
+    // If the entity is new but a config file for it already exists, prevent
+    // it to be overwritten.
+    if ($entity->isNew() && !$config->isNew()) {
+      throw new EntityStorageException(String::format('@type entity with ID @id already exists.', array('@type' => $this->entityType, '@id' => $id)));
+    }
+
     if (!$is_new && !isset($entity->original)) {
       $this->resetCache(array($id));
       $entity->original = $this->load($id);
diff --git a/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php b/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
index 260da45..e72ed99 100644
--- a/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
+++ b/core/modules/comment/lib/Drupal/comment/Tests/CommentPreviewTest.php
@@ -31,28 +31,6 @@ public static function getInfo() {
     );
   }
 
-  function setUp() {
-    parent::setUp();
-
-    // Add the basic_html filter format from the standard install profile.
-    $filter_format_storage_controller = $this->container->get('entity.manager')->getStorageController('filter_format');
-    $filter_format = $filter_format_storage_controller->create(array(
-      'format' => 'basic_html',
-      'name' => 'Basic HTML',
-      'status' => TRUE,
-      'roles' => array('authenticated'),
-    ), 'filter_format');
-
-    $filter_format->setFilterConfig('filter_html', array(
-      'module' => 'filter',
-      'status' => TRUE,
-      'settings' => array(
-        'allowed_html' => '<a> <em> <strong> <cite> <blockquote> <code> <ul> <ol> <li> <dl> <dt> <dd> <h4> <h5> <h6> <p> <span> <img>',
-      ),
-    ));
-    $filter_format->save();
-  }
-
   /**
    * Tests comment preview.
    */
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
index 9acca96..955177e 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\config\Tests;
 
 use Drupal\Core\Entity\EntityMalformedException;
+use Drupal\Core\Entity\EntityStorageException;
 use Drupal\Core\Language\Language;
 use Drupal\simpletest\WebTestBase;
 
@@ -135,24 +136,18 @@ function testCRUD() {
     $this->assertIdentical($config_test->isNew(), FALSE);
     $this->assertIdentical($config_test->getOriginalId(), $expected['id']);
 
-    // Re-create the entity with the same ID and verify updated status.
+    // Make sure that is not possible to overwrite an existing entity with
+    // a new one.
     $same_id = entity_create('config_test', array(
       'id' => $config_test->id(),
     ));
     $this->assertIdentical($same_id->isNew(), TRUE);
-    $status = $same_id->save();
-    $this->assertIdentical($status, SAVED_UPDATED);
-
-    // Verify that the entity was overwritten.
-    $same_id = entity_load('config_test', $config_test->id());
-    $this->assertIdentical($same_id->id(), $config_test->id());
-    $this->assertIdentical($same_id->label(), NULL);
-    $this->assertNotEqual($same_id->uuid(), $config_test->uuid());
-
-    // Delete the overridden entity first.
-    $same_id->delete();
-    // Revert to previous state.
-    $config_test->save();
+    try {
+      $same_id->save();
+      $this->fail('Not possible to overwrite an entity entity.');
+    } catch (EntityStorageException $e) {
+      $this->pass('Not possible to overwrite an entity entity.');
+    }
 
     // Verify that renaming the ID returns correct status and properties.
     $ids = array($expected['id'], 'second_' . $this->randomName(4), 'third_' . $this->randomName(4));
diff --git a/core/modules/field/lib/Drupal/field/Entity/Field.php b/core/modules/field/lib/Drupal/field/Entity/Field.php
index b127979..6d5e68a 100644
--- a/core/modules/field/lib/Drupal/field/Entity/Field.php
+++ b/core/modules/field/lib/Drupal/field/Entity/Field.php
@@ -316,12 +316,6 @@ protected function preSaveNew(EntityStorageControllerInterface $storage_controll
       ));
     }
 
-    // Ensure the field name is unique (we do not care about deleted fields).
-    if ($prior_field = $storage_controller->load($this->id)) {
-      $message = 'Attempt to create field name %name which already exists.';
-      throw new FieldException(format_string($message, array('%name' => $this->name)));
-    }
-
     // Disallow reserved field names. This can't prevent all field name
     // collisions with existing entity properties, but some is better than
     // none.
diff --git a/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php b/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php
index 7c2e381..51eebbd 100644
--- a/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php
+++ b/core/modules/field/lib/Drupal/field/Entity/FieldInstance.php
@@ -346,10 +346,6 @@ public function preSave(EntityStorageControllerInterface $storage_controller) {
     $field_type_manager = \Drupal::service('plugin.manager.field.field_type');
 
     if ($this->isNew()) {
-      // Ensure the field instance is unique within the bundle.
-      if ($prior_instance = $storage_controller->load($this->id())) {
-        throw new FieldException(format_string('Attempt to create an instance of field %name on bundle @bundle that already has an instance of that field.', array('%name' => $this->field->name, '@bundle' => $this->bundle)));
-      }
       // Set the default instance settings.
       $this->settings += $field_type_manager->getDefaultInstanceSettings($this->field->type);
       // Notify the entity storage controller.
diff --git a/core/modules/field/lib/Drupal/field/Tests/CrudTest.php b/core/modules/field/lib/Drupal/field/Tests/CrudTest.php
index 73ee608..b7e9209 100644
--- a/core/modules/field/lib/Drupal/field/Tests/CrudTest.php
+++ b/core/modules/field/lib/Drupal/field/Tests/CrudTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\field\Tests;
 
+use Drupal\Core\Entity\EntityStorageException;
 use Drupal\field\FieldException;
 
 class CrudTest extends FieldUnitTestBase {
@@ -70,7 +71,7 @@ function testCreateField() {
       entity_create('field_entity', $field_definition)->save();
       $this->fail(t('Cannot create two fields with the same name.'));
     }
-    catch (FieldException $e) {
+    catch (EntityStorageException $e) {
       $this->pass(t('Cannot create two fields with the same name.'));
     }
 
diff --git a/core/modules/field/lib/Drupal/field/Tests/FieldInstanceCrudTest.php b/core/modules/field/lib/Drupal/field/Tests/FieldInstanceCrudTest.php
index e05baac..9eaa8d0 100644
--- a/core/modules/field/lib/Drupal/field/Tests/FieldInstanceCrudTest.php
+++ b/core/modules/field/lib/Drupal/field/Tests/FieldInstanceCrudTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\field\Tests;
 
+use Drupal\Core\Entity\EntityStorageException;
 use Drupal\field\FieldException;
 
 class FieldInstanceCrudTest extends FieldUnitTestBase {
@@ -90,7 +91,7 @@ function testCreateFieldInstance() {
       entity_create('field_instance', $this->instance_definition)->save();
       $this->fail(t('Cannot create two instances with the same field / bundle combination.'));
     }
-    catch (FieldException $e) {
+    catch (EntityStorageException $e) {
       $this->pass(t('Cannot create two instances with the same field / bundle combination.'));
     }
 
diff --git a/core/modules/node/tests/modules/node_test_views/test_views/views.view.test_field_type.yml b/core/modules/node/tests/modules/node_test_views/test_views/views.view.test_field_type.yml
index e6382e4..6113c52 100644
--- a/core/modules/node/tests/modules/node_test_views/test_views/views.view.test_field_type.yml
+++ b/core/modules/node/tests/modules/node_test_views/test_views/views.view.test_field_type.yml
@@ -10,6 +10,7 @@ display:
           field: type
           id: type
           table: node_field_data
+          plugin_id: node_type
           provider: node
     display_plugin: default
     display_title: Master
diff --git a/core/modules/views/lib/Drupal/views/Tests/ViewStorageTest.php b/core/modules/views/lib/Drupal/views/Tests/ViewStorageTest.php
index 70df481..4fc2f5c 100644
--- a/core/modules/views/lib/Drupal/views/Tests/ViewStorageTest.php
+++ b/core/modules/views/lib/Drupal/views/Tests/ViewStorageTest.php
@@ -142,6 +142,8 @@ protected function createTests() {
 
     // Create a new View instance with config values.
     $values = \Drupal::config('views.view.test_view_storage')->get();
+    $values['id'] = 'test_view_storage_new';
+    unset($values['uuid']);
     $created = $this->controller->create($values);
 
     $this->assertTrue($created instanceof View, 'Created object is a View.');
@@ -157,7 +159,6 @@ protected function createTests() {
     }
 
     // Check the UUID of the loaded View.
-    $created->set('id', 'test_view_storage_new');
     $created->save();
     $created_loaded = entity_load('view', 'test_view_storage_new');
     $this->assertIdentical($created->uuid(), $created_loaded->uuid(), 'The created UUID has been saved correctly.');
diff --git a/core/modules/views/tests/modules/views_test_config/test_views/views.view.test_field_type.yml b/core/modules/views/tests/modules/views_test_config/test_views/views.view.test_field_type.yml
deleted file mode 100644
index 6113c52..0000000
--- a/core/modules/views/tests/modules/views_test_config/test_views/views.view.test_field_type.yml
+++ /dev/null
@@ -1,21 +0,0 @@
-base_table: node
-core: '8'
-description: ''
-status: '1'
-display:
-  default:
-    display_options:
-      fields:
-        type:
-          field: type
-          id: type
-          table: node_field_data
-          plugin_id: node_type
-          provider: node
-    display_plugin: default
-    display_title: Master
-    id: default
-    position: '0'
-label: ''
-id: test_field_type
-tag: ''