diff --git a/core/lib/Drupal/Core/Entity/EntityNG.php b/core/lib/Drupal/Core/Entity/EntityNG.php
index f6d44ba..427fe68 100644
--- a/core/lib/Drupal/Core/Entity/EntityNG.php
+++ b/core/lib/Drupal/Core/Entity/EntityNG.php
@@ -440,7 +440,7 @@ public function __set($name, $value) {
    */
   public function __isset($name) {
     if ($this->getPropertyDefinition($name)) {
-      return (bool) count($this->get($name));
+      return $this->get($name)->getValue() !== NULL;
     }
     else {
       return isset($this->values[$name]);
diff --git a/core/lib/Drupal/Core/Entity/Field/Type/Field.php b/core/lib/Drupal/Core/Entity/Field/Type/Field.php
index 5daa81f..06e3564 100644
--- a/core/lib/Drupal/Core/Entity/Field/Type/Field.php
+++ b/core/lib/Drupal/Core/Entity/Field/Type/Field.php
@@ -38,13 +38,6 @@ class Field extends ContextAwareTypedData implements IteratorAggregate, FieldInt
   protected $list = array();
 
   /**
-   * Flag to indicate if this field has been set.
-   *
-   * @var bool
-   */
-  protected $isset = FALSE;
-
-  /**
    * Overrides ContextAwareTypedData::__construct().
    */
   public function __construct(array $definition, $name = NULL, ContextAwareInterface $parent = NULL) {
@@ -60,16 +53,18 @@ public function __construct(array $definition, $name = NULL, ContextAwareInterfa
    * Implements TypedDataInterface::getValue().
    */
   public function getValue() {
-    $values = array();
-    foreach ($this->list as $delta => $item) {
-      if (!$item->isEmpty()) {
-        $values[$delta] = $item->getValue();
-      }
-      else {
-        $values[$delta] = NULL;
+    if (isset($this->list)) {
+      $values = array();
+      foreach ($this->list as $delta => $item) {
+        if (!$item->isEmpty()) {
+          $values[$delta] = $item->getValue();
+        }
+        else {
+          $values[$delta] = NULL;
+        }
       }
+      return $values;
     }
-    return $values;
   }
 
   /**
@@ -79,7 +74,6 @@ public function getValue() {
    *   An array of values of the field items.
    */
   public function setValue($values) {
-    $this->isset = TRUE;
     if (isset($values) && $values !== array()) {
       // Support passing in only the value of the first item.
       if (!is_array($values) || !is_numeric(current(array_keys($values)))) {
@@ -87,7 +81,9 @@ public function setValue($values) {
       }
 
       // Clear the values of properties for which no value has been passed.
-      $this->list = array_intersect_key($this->list, $values);
+      if (isset($this->list)) {
+        $this->list = array_intersect_key($this->list, $values);
+      }
 
       // Set the values.
       foreach ($values as $delta => $value) {
@@ -102,17 +98,12 @@ public function setValue($values) {
         }
       }
     }
-    else {
+    elseif ($values === array()) {
       $this->list = array();
     }
-  }
-
-  /**
-   * Mark this field as not set.
-   */
-  public function unsetValue() {
-    $this->list = array();
-    $this->isset = FALSE;
+    else {
+      $this->list = NULL;
+    }
   }
 
   /**
@@ -122,10 +113,12 @@ public function unsetValue() {
    */
   public function getString() {
     $strings = array();
-    foreach ($this->list() as $item) {
-      $strings[] = $item->getString();
+    if (isset($this->list)) {
+      foreach ($this->list() as $item) {
+        $strings[] = $item->getString();
+      }
+      return implode(', ', array_filter($strings));
     }
-    return implode(', ', array_filter($strings));
   }
 
   /**
@@ -139,14 +132,16 @@ public function validate() {
    * Implements ArrayAccess::offsetExists().
    */
   public function offsetExists($offset) {
-    return array_key_exists($offset, $this->list);
+    return isset($this->list) && array_key_exists($offset, $this->list);
   }
 
   /**
    * Implements ArrayAccess::offsetUnset().
    */
   public function offsetUnset($offset) {
-    unset($this->list[$offset]);
+    if (isset($this->list)) {
+      unset($this->list[$offset]);
+    }
   }
 
   /**
@@ -204,14 +199,17 @@ public function offsetSet($offset, $value) {
    * Implements IteratorAggregate::getIterator().
    */
   public function getIterator() {
-    return new ArrayIterator($this->list);
+    if (isset($this->list)) {
+      return new ArrayIterator($this->list);
+    }
+    return new ArrayIterator(array());
   }
 
   /**
    * Implements Countable::count().
    */
   public function count() {
-    return count($this->list);
+    return isset($this->list) ? count($this->list) : 0;
   }
 
   /**
@@ -247,14 +245,13 @@ public function get($property_name) {
    */
   public function __set($property_name, $value) {
     $this->offsetGet(0)->__set($property_name, $value);
-    $this->isset = TRUE;
   }
 
   /**
    * Delegate.
    */
   public function __isset($property_name) {
-    return $this->isset && $this->offsetGet(0)->__isset($property_name);
+    return $this->offsetGet(0)->__isset($property_name);
   }
 
   /**
@@ -268,31 +265,26 @@ public function __unset($property_name) {
    * Implements ListInterface::isEmpty().
    */
   public function isEmpty() {
-    foreach ($this->list as $item) {
-      if (!$item->isEmpty()) {
-        return FALSE;
+    if (isset($this->list)) {
+      foreach ($this->list as $item) {
+        if (!$item->isEmpty()) {
+          return FALSE;
+        }
       }
     }
     return TRUE;
   }
 
   /**
-   * Determines if this field has been set.
-   *
-   * @return bool
-   */
-  public function valueIsSet() {
-    return $this->isset;
-  }
-
-  /**
    * Implements a deep clone.
    */
   public function __clone() {
-    foreach ($this->list as $delta => $property) {
-      $this->list[$delta] = clone $property;
-      if ($property instanceof ContextAwareInterface) {
-        $this->list[$delta]->setContext($delta, $this);
+    if (isset($this->list)) {
+      foreach ($this->list as $delta => $property) {
+        $this->list[$delta] = clone $property;
+        if ($property instanceof ContextAwareInterface) {
+          $this->list[$delta]->setContext($delta, $this);
+        }
       }
     }
   }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Entity/EntityFieldTest.php b/core/modules/system/lib/Drupal/system/Tests/Entity/EntityFieldTest.php
index c69b90f..56f3873 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Entity/EntityFieldTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Entity/EntityFieldTest.php
@@ -226,7 +226,7 @@ public function testReadWrite() {
     // Test removing all list items by setting it to NULL.
     $entity->name = NULL;
     $this->assertIdentical(count($entity->name), 0, 'Name field contains no items.');
-    $this->assertIdentical($entity->name->getValue(), array(), 'Name field value is an empty array.');
+    $this->assertNull($entity->name->getValue(), 'Name field value is NULL.');
 
     // Test get and set field values.
     $entity->name = 'foo';