diff --git a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
index 60c36b5..56260e6 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
@@ -9,7 +9,6 @@
 
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Field\FieldDefinitionInterface;
-use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -299,8 +298,10 @@ protected function invokeFieldMethod($method, ContentEntityInterface $entity) {
    *   Specifies whether the entity is being updated or created.
    */
   protected function invokeFieldPostSave(ContentEntityInterface $entity, $update) {
+    // For each entity translation this returns an array of resave flags keyed
+    // by field name, thus we merge them to obtain a list of fields to resave.
     $resave = [];
-    foreach ($this->invokeFieldMethod('postSave', $entity, $update) as $langcode => $results) {
+    foreach ($this->invokeFieldMethod('postSave', $entity, $update) as $results) {
       $resave += array_filter($results);
     }
     if ($resave) {
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php
index 937cb5f..927a946 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php
@@ -936,10 +936,10 @@ public function save(EntityInterface $entity) {
    */
   protected function doSaveFieldItems(ContentEntityInterface $entity, array $names = []) {
     if (!$names) {
-      $this->doRegularSave($entity);
+      $this->doSaveFieldItemsFull($entity);
     }
     else {
-      $this->doResaveFieldItems($entity, $names);
+      $this->doSaveFieldItemsPartial($entity, $names);
     }
   }
 
@@ -951,7 +951,7 @@ protected function doSaveFieldItems(ContentEntityInterface $entity, array $names
    *
    * @internal
    */
-  protected function doRegularSave(ContentEntityInterface $entity) {
+  protected function doSaveFieldItemsFull(ContentEntityInterface $entity) {
     // Create the storage record to be saved.
     $record = $this->mapToStorageRecord($entity);
 
@@ -1001,7 +1001,7 @@ protected function doRegularSave(ContentEntityInterface $entity) {
   }
 
   /**
-   * Resaves a set of entity fields to the database.
+   * Saves a set of entity fields to the database.
    *
    * @param \Drupal\Core\Entity\ContentEntityInterface $entity
    *   The entity object.
@@ -1010,7 +1010,7 @@ protected function doRegularSave(ContentEntityInterface $entity) {
    *
    * @internal
    */
-  protected function doResaveFieldItems(ContentEntityInterface $entity, array $names) {
+  protected function doSaveFieldItemsPartial(ContentEntityInterface $entity, array $names) {
     $table_mapping = $this->getTableMapping();
     $storage_definitions = $this->entityManager->getFieldStorageDefinitions($this->entityTypeId);
     $shared_table_fields = FALSE;
diff --git a/core/lib/Drupal/Core/Field/FieldItemBase.php b/core/lib/Drupal/Core/Field/FieldItemBase.php
index c1441bb..8e50c6a 100644
--- a/core/lib/Drupal/Core/Field/FieldItemBase.php
+++ b/core/lib/Drupal/Core/Field/FieldItemBase.php
@@ -201,9 +201,7 @@ public function preSave() { }
   /**
    * {@inheritdoc}
    */
-  public function postSave($update) {
-    return FALSE;
-  }
+  public function postSave($update) { }
 
   /**
    * {@inheritdoc}
diff --git a/core/modules/file/src/Plugin/Field/FieldType/FileFieldItemList.php b/core/modules/file/src/Plugin/Field/FieldType/FileFieldItemList.php
index 033a742..8b0aac1 100644
--- a/core/modules/file/src/Plugin/Field/FieldType/FileFieldItemList.php
+++ b/core/modules/file/src/Plugin/Field/FieldType/FileFieldItemList.php
@@ -73,8 +73,6 @@ public function postSave($update) {
         }
       }
     }
-
-    return FALSE;
   }
 
   /**
diff --git a/core/modules/path/src/Plugin/Field/FieldType/PathItem.php b/core/modules/path/src/Plugin/Field/FieldType/PathItem.php
index 9ad35ac..4bfe0d0 100644
--- a/core/modules/path/src/Plugin/Field/FieldType/PathItem.php
+++ b/core/modules/path/src/Plugin/Field/FieldType/PathItem.php
@@ -75,7 +75,6 @@ public function postSave($update) {
         \Drupal::service('path.alias_storage')->save($entity->urlInfo()->getInternalPath(), $this->alias, $this->getLangcode(), $this->pid);
       }
     }
-    return FALSE;
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Field/FieldItemTest.php b/core/modules/system/src/Tests/Field/FieldItemTest.php
new file mode 100644
index 0000000..b89b706
--- /dev/null
+++ b/core/modules/system/src/Tests/Field/FieldItemTest.php
@@ -0,0 +1,98 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\system\Tests\Field\FieldItemTest.
+ */
+
+namespace Drupal\system\Tests\Field;
+
+use Drupal\Component\Utility\Unicode;
+use Drupal\entity_test\Entity\EntityTest;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\system\Tests\Entity\EntityUnitTestBase;
+
+/**
+ * Test field item methods.
+ *
+ * @group Field
+ */
+class FieldItemTest extends EntityUnitTestBase {
+
+  /**
+   * @var string
+   */
+  protected $fieldName;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->fieldName = Unicode::strtolower($this->randomMachineName());
+    $entity_type_id = 'entity_test';
+
+    /** @var \Drupal\field\Entity\FieldStorageConfig $field_storage */
+    FieldStorageConfig::create([
+      'field_name' => $this->fieldName,
+      'type' => 'field_test',
+      'entity_type' => $entity_type_id,
+      'cardinality' => 1,
+    ])->save();
+
+    FieldConfig::create([
+      'entity_type' => $entity_type_id,
+      'field_name' => $this->fieldName,
+      'bundle' => $entity_type_id,
+      'label' => 'Test field',
+    ])->save();
+
+    $this->entityManager->clearCachedDefinitions();
+    $definitions = $this->entityManager->getFieldStorageDefinitions('entity_test');
+    $this->assertTrue(!empty($definitions[$this->fieldName]));
+  }
+
+  /**
+   * Tests the field item save workflow.
+   */
+  public function testSaveWorkflow() {
+    $entity = EntityTest::create([
+      'name' => $this->randomString(),
+      $this->fieldName => $this->randomString(),
+    ]);
+
+    // Save a new entity and verify that the initial field value is overwritten
+    // with a value containing the entity id, which implies a resave. Check that
+    // the entity data structure and the stored values match.
+    $this->assertSavedFieldItemValue($entity, "field_test:{$this->fieldName}:1:1");
+
+    // Update the entity and verify that the field value is overwritten on
+    // presave if it is not resaved.
+    $this->assertSavedFieldItemValue($entity, 'overwritten');
+
+    // Flag the field value as needing to be resaved and verify it actually is.
+    $entity->{$this->fieldName}->value = 'resave';
+    $this->assertSavedFieldItemValue($entity, "field_test:{$this->fieldName}:1:3");
+  }
+
+  /**
+   * Checks that the saved field item value matches the expected one.
+   *
+   * @param \Drupal\entity_test\Entity\EntityTest $entity
+   *   The test entity.
+   * @param $expected_value
+   *   The expected field item value.
+   *
+   * @return bool
+   *   TRUE if the item value matches expectations, FALSE otherwise.
+   */
+  protected function assertSavedFieldItemValue(EntityTest $entity, $expected_value) {
+    $entity->save();
+    $result = $this->assertEqual($entity->{$this->fieldName}->value, $expected_value);
+    $entity = $this->reloadEntity($entity);
+    return $result && $this->assertEqual($entity->{$this->fieldName}->value, $expected_value);
+  }
+
+}
diff --git a/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/FieldTestItem.php b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/FieldTestItem.php
new file mode 100644
index 0000000..9e8dc74
--- /dev/null
+++ b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/FieldTestItem.php
@@ -0,0 +1,105 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\entity_test\Plugin\Field\FieldType\FieldTestItem.
+ */
+
+namespace Drupal\entity_test\Plugin\Field\FieldType;
+
+use Drupal\Core\Field\FieldItemBase;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\Core\StringTranslation\TranslationWrapper;
+use Drupal\Core\TypedData\DataDefinition;
+
+
+/**
+ * Defines the 'field_test' entity field type.
+ *
+ * @FieldType(
+ *   id = "field_test",
+ *   label = @Translation("Test field item"),
+ *   description = @Translation("A field containing a plain string value."),
+ *   category = @Translation("Field"),
+ * )
+ */
+class FieldTestItem extends FieldItemBase {
+
+  /**
+   * Counts how many times the item is saved.
+   *
+   * @var int
+   */
+  protected static $counter = 0;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
+    // This is called very early by the user entity roles field. Prevent
+    // early t() calls by using the TranslationWrapper.
+    $properties['value'] = DataDefinition::create('string')
+      ->setLabel(new TranslationWrapper('Test value'))
+      ->setRequired(TRUE);
+
+    return $properties;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function schema(FieldStorageDefinitionInterface $field_definition) {
+    return array(
+      'columns' => array(
+        'value' => array(
+          'type' => 'varchar',
+          'length' => 255,
+        ),
+      ),
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function preSave() {
+    static::$counter++;
+
+    // Overwrite the field value unless it is going to be overridden, in which
+    // case its final value will already be different from the current one.
+    if (!$this->getEntity()->isNew() && !$this->mustResave()) {
+      $this->setValue('overwritten');
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function postSave($update) {
+    // Determine whether the field value should be rewritten to the storage. We
+    // always rewrite on create as we need to store a value including the entity
+    // id.
+    $resave = !$update || $this->mustResave();
+
+    if ($resave) {
+      $entity = $this->getEntity();
+      $definition = $this->getFieldDefinition();
+      $field_name = $definition->getName();
+      $value = 'field_test:' . $field_name . ':' . $entity->id() . ':' . static::$counter;
+      $this->setValue($value);
+    }
+
+    return $resave;
+  }
+
+  /**
+   * Checks whether the field item value should be resaved.
+   *
+   * @return bool
+   *   TRUE if the item should be resaved, FALSE otherwise.
+   */
+  protected function mustResave() {
+    return $this->getValue()['value'] == 'resave';
+  }
+
+}