diff --git a/core/lib/Drupal/Core/Field/FieldItemBase.php b/core/lib/Drupal/Core/Field/FieldItemBase.php
index b411b88..37b2dc4 100644
--- a/core/lib/Drupal/Core/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Field/FieldItemBase.php
@@ -51,6 +51,17 @@ public static function mainPropertyName() {
    */
   public function __construct(DataDefinitionInterface $definition, $name = NULL, TypedDataInterface $parent = NULL) {
     parent::__construct($definition, $name, $parent);
+    // Data types such as Integer or String use a simple value property to
+    // manage their value, which is why TypedData::getValue() uses that property
+    // for convencience of those data types. By declaring it as a member
+    // variable of the TypedData class, however, PHP sets a NULL value to it
+    // upon instantiation. This breaks field types which have a 'value' property
+    // as by inheriting from this class they inherit from TypedData as well and,
+    // thus, $field_item->value returns NULL directly instead of asking
+    // FieldItemBase::__get() for the proper value stored in
+    // $field_item->values['value']. Hence, we unset the NULL value.
+    unset($this->value);
+
     // Initialize computed properties by default, such that they get cloned
     // with the whole item.
     foreach ($this->definition->getPropertyDefinitions() as $name => $definition) {
diff --git a/core/lib/Drupal/Core/TypedData/TypedData.php b/core/lib/Drupal/Core/TypedData/TypedData.php
index 3216d21..bd7caa7 100644
--- a/core/lib/Drupal/Core/TypedData/TypedData.php
+++ b/core/lib/Drupal/Core/TypedData/TypedData.php
@@ -44,6 +44,13 @@
   protected $parent;
 
   /**
+   * The configuration value.
+   *
+   * @var mixed
+   */
+  protected $value;
+
+  /**
    * {@inheritdoc}
    */
   public static function createInstance($definition, $name = NULL, TraversableTypedDataInterface $parent = NULL) {