diff -u b/core/modules/migrate_drupal/src/Tests/d6/EntityContentBaseTest.php b/core/modules/migrate_drupal/src/Tests/d6/EntityContentBaseTest.php
--- b/core/modules/migrate_drupal/src/Tests/d6/EntityContentBaseTest.php
+++ b/core/modules/migrate_drupal/src/Tests/d6/EntityContentBaseTest.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\migrate_drupal\Tests\d6;
 
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\migrate\Entity\Migration;
 use Drupal\user\Entity\User;
 
@@ -21,20 +23,41 @@
   public function setUp() {
     parent::setUp();
 
+    // Create a field on the user entity so that we can test nested property
+    // overwrites.
+    // @see static::testOverwriteSelectedNestedProperty()
+    FieldStorageConfig::create([
+      'field_name' => 'signature',
+      'entity_type' => 'user',
+      'type' => 'text_long',
+    ])->save();
+
+    FieldConfig::create([
+      'field_name' => 'signature',
+      'entity_type' => 'user',
+      'bundle' => 'user',
+    ])->save();
+
     User::create([
       'uid' => 2,
-      'name' => 'Michael Palin',
-      'mail' => 'mike@monty.py',
+      'name' => 'Ford Prefect',
+      'mail' => 'ford.prefect@localhost',
+      'signature' => array(
+        array(
+          'value' => 'Bring a towel.',
+          'format' => 'filtered_html',
+        ),
+      ),
     ])->save();
 
     $this->executeMigrations(['d6_filter_format', 'd6_user_role']);
   }
 
   /**
-   * Tests overwriting all properties in the destination entity (default
+   * Tests overwriting all mapped properties in the destination entity (default
    * behavior).
    */
-  public function testOverwriteAllProperties() {
+  public function testOverwriteAllMappedProperties() {
     $this->executeMigration('d6_user');
     /** @var \Drupal\user\UserInterface $account */
     $account = User::load(2);
@@ -55,8 +78,34 @@
 
     /** @var \Drupal\user\UserInterface $account */
     $account = User::load(2);
-    $this->assertIdentical('Michael Palin', $account->label());
+    $this->assertIdentical('Ford Prefect', $account->label());
     $this->assertIdentical('john.doe@example.com', $account->getEmail());
+    $this->assertIdentical('Bring a towel.', $account->signature->value);
+  }
+
+  /**
+   * Tests overwriting selected nested properties in the destination entity,
+   * specified in the destination configuration.
+   */
+  public function testOverwriteSelectedNestedProperty() {
+    /** @var \Drupal\migrate\Entity\MigrationInterface $migration */
+    $migration = Migration::load('d6_user');
+    $destination = $migration->get('destination');
+    // Migrate a static value into the signature, and ignore everything else.
+    $destination['overwrite_properties'][] = 'signature/value';
+    $migration->set('destination', $destination);
+    $process = array(
+      'plugin' => 'default_value',
+      'default_value' => 'The answer is 42.',
+    );
+    $migration->setProcessOfProperty('signature/value', $process);
+    $this->executeMigration($migration);
+
+    /** @var \Drupal\user\UserInterface $account */
+    $account = User::load(2);
+    $this->assertIdentical('Ford Prefect', $account->label());
+    $this->assertIdentical('ford.prefect@localhost', $account->getEmail());
+    $this->assertIdentical('The answer is 42.', $account->signature->value);
   }
 
 }