diff --git a/core/modules/serialization/src/Collection.php b/core/modules/serialization/src/Collection.php
index e3fd9aa..7f3d922 100644
--- a/core/modules/serialization/src/Collection.php
+++ b/core/modules/serialization/src/Collection.php
@@ -23,7 +23,7 @@ class Collection implements \IteratorAggregate {
    *
    * @var array
    */
-  protected $items = [];
+  protected $items;
 
   /**
    * The title of the collection.
diff --git a/core/modules/serialization/tests/src/Unit/CollectionTest.php b/core/modules/serialization/tests/src/Unit/CollectionTest.php
index 52ccd5b..9c66275 100644
--- a/core/modules/serialization/tests/src/Unit/CollectionTest.php
+++ b/core/modules/serialization/tests/src/Unit/CollectionTest.php
@@ -68,7 +68,7 @@ public function testConstructor() {
   public function testSettingItemsAndIterating() {
     $collection = new Collection('example');
 
-    $this->assertEquals($collection->getItems(), NULL, 'By default the  items are NULL');
+    $this->assertEquals($collection->getItems(), NULL, 'By default the items are NULL');
 
     $example = array(1, 2, 3);
     $collection->setItems($example);