diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
index 95089f7..66984cd 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
@@ -194,4 +194,13 @@ function testUpdated() {
     $this->assertFalse(config_sync_get_changes($staging, $storage));
   }
 
+  /**
+   * Tests enabling a module with a duplicate configuration entity.
+   */
+  function testDuplicate() {
+    $this->assertEqual(config('config_test.dynamic.default')->get('label'), 'Default', "Configuration object label is 'Default'.");
+    module_enable(array('config_test_duplicate'));
+    $this->assertEqual(config('config_test.dynamic.default')->get('label'), 'Default', 'Configuration object is not silently overwritten on import.');
+  }
+
 }
diff --git a/core/modules/config/tests/config_test_duplicate/config/config_test.dynamic.default.yml b/core/modules/config/tests/config_test_duplicate/config/config_test.dynamic.default.yml
new file mode 100644
index 0000000..12efb31
--- /dev/null
+++ b/core/modules/config/tests/config_test_duplicate/config/config_test.dynamic.default.yml
@@ -0,0 +1,2 @@
+id: default
+label: Not default
diff --git a/core/modules/config/tests/config_test_duplicate/config_test_duplicate.info b/core/modules/config/tests/config_test_duplicate/config_test_duplicate.info
new file mode 100644
index 0000000..491708d
--- /dev/null
+++ b/core/modules/config/tests/config_test_duplicate/config_test_duplicate.info
@@ -0,0 +1,5 @@
+name = Duplicate default configuration
+package = Core
+version = VERSION
+core = 8.x
+hidden = TRUE
diff --git a/core/modules/config/tests/config_test_duplicate/config_test_duplicate.module b/core/modules/config/tests/config_test_duplicate/config_test_duplicate.module
new file mode 100644
index 0000000..f6c2685
--- /dev/null
+++ b/core/modules/config/tests/config_test_duplicate/config_test_duplicate.module
@@ -0,0 +1,6 @@
+<?php
+
+/**
+ * @file
+ * Test module with a duplicate of a config_test configuration entity.
+ */