diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
index 285d087..56603c7 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
@@ -272,17 +272,19 @@ public static function sort(ConfigEntityInterface $a, ConfigEntityInterface $b)
    */
   public function toArray() {
     $properties = array();
+    /** @var \Drupal\Core\Config\Entity\ConfigEntityTypeInterface $entity_type */
     $entity_type = $this->getEntityType();
-    $config_name = $entity_type->getConfigPrefix() . '.' . $this->id();
 
     $properties_to_export = $entity_type->getPropertiesToExport();
     if (empty($properties_to_export)) {
+      $config_name = $entity_type->getConfigPrefix() . '.' . $this->id();
       $definition = $this->getTypedConfig()->getDefinition($config_name);
       if (!isset($definition['mapping'])) {
         throw new SchemaIncompleteException(SafeMarkup::format('Incomplete or missing schema for @config_name', array('@config_name' => $config_name)));
       }
       $properties_to_export = array_combine(array_keys($definition['mapping']), array_keys($definition['mapping']));
     }
+
     $id_key = $entity_type->getKey('id');
     foreach ($properties_to_export as $property_name => $export_name) {
       // Special handling for IDs so that computed compound IDs work.
@@ -294,6 +296,7 @@ public function toArray() {
         $properties[$export_name] = $this->get($property_name);
       }
     }
+
     if (empty($this->third_party_settings)) {
       unset($properties['third_party_settings']);
     }
diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityType.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityType.php
index 618690d..f15eef5 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityType.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityType.php
@@ -74,7 +74,6 @@ public function __construct($definition) {
     $this->handlers += array(
       'storage' => 'Drupal\Core\Config\Entity\ConfigEntityStorage',
     );
-
   }
 
   /**
@@ -175,7 +174,7 @@ public function getPropertiesToExport() {
           'langcode' => 'langcode',
           'status' => 'status',
           'dependencies' => 'dependencies',
-          'third_party_settings' => 'third_party_settings'
+          'third_party_settings' => 'third_party_settings',
         ];
         foreach ($this->config_export as $property => $name) {
           if (is_numeric($property)) {
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
index c71a7e5..5e11828 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
@@ -476,6 +476,31 @@ public function testToArray() {
   /**
    * @covers ::toArray
    */
+  public function testToArrayIdKey() {
+    $entity = $this->getMockForAbstractClass('\Drupal\Core\Config\Entity\ConfigEntityBase', [[], $this->entityTypeId], '', TRUE, TRUE, TRUE, ['id', 'get']);
+    $entity->expects($this->exactly(3))
+      ->method('id')
+      ->willReturn($this->id);
+    $entity->expects($this->once())
+      ->method('get')
+      ->willReturn([]);
+    $this->typedConfigManager->expects($this->never())
+      ->method('getDefinition');
+    $this->entityType->expects($this->any())
+      ->method('getPropertiesToExport')
+      ->willReturn(['id' => 'configId', 'dependencies' => 'dependencies']);
+    $this->entityType->expects($this->once())
+      ->method('getKey')
+      ->with('id')
+      ->willReturn('id');
+    $properties = $entity->toArray();
+    $this->assertInternalType('array', $properties);
+    $this->assertEquals(['configId' => $entity->id(), 'dependencies' => []], $properties);
+  }
+
+  /**
+   * @covers ::toArray
+   */
   public function testToArraySchemaFallback() {
     $this->typedConfigManager->expects($this->once())
       ->method('getDefinition')
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php
index b427dfc..524fea0 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityTypeTest.php
@@ -131,4 +131,60 @@ public function providerTestGetConfigPrefix() {
     );
   }
 
+  /**
+   * @covers ::getPropertiesToExport
+   *
+   * @dataProvider providerGetPropertiesToExport
+   */
+  public function testGetPropertiesToExport($definition, $expected) {
+    $entity_type = $this->setUpConfigEntityType($definition);
+    $properties_to_export = $entity_type->getPropertiesToExport();
+    $this->assertSame($expected, $properties_to_export);
+
+    // Ensure the method is idempotent.
+    $properties_to_export = $entity_type->getPropertiesToExport();
+    $this->assertSame($expected, $properties_to_export);
+  }
+
+  public function providerGetPropertiesToExport() {
+    $data = [];
+    $data[] = [
+      [],
+      NULL,
+    ];
+
+    $data[] = [
+      [
+        'config_export' => [
+          'id',
+          'custom_property' => 'customProperty',
+        ],
+      ],
+      [
+        'uuid' => 'uuid',
+        'langcode' => 'langcode',
+        'status' => 'status',
+        'dependencies' => 'dependencies',
+        'third_party_settings' => 'third_party_settings',
+        'id' => 'id',
+        'custom_property' => 'customProperty',
+      ],
+    ];
+
+    $data[] = [
+      [
+        'config_export' => [
+          'id',
+        ],
+        'mergedConfigExport' => [
+          'random_key' => 'random_key',
+        ],
+      ],
+      [
+        'random_key' => 'random_key',
+      ],
+    ];
+    return $data;
+  }
+
 }