diff --git a/core/lib/Drupal/Core/Entity/EntityManager.php b/core/lib/Drupal/Core/Entity/EntityManager.php
index f0fcac8..76582bb 100644
--- a/core/lib/Drupal/Core/Entity/EntityManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityManager.php
@@ -471,13 +471,24 @@ protected function buildBaseFieldDefinitions($entity_type_id) {
 
     // Ensure defined entity keys are there and have proper revisionable and
     // translatable values.
-    $fixed_keys = array('id', 'revision', 'uuid', 'bundle');
-    foreach ($keys as $key => $field_name) {
-      if (isset($base_field_definitions[$field_name]) && in_array($key, $fixed_keys) && $base_field_definitions[$field_name]->isRevisionable()) {
-        throw new \LogicException(String::format('The @field field cannot be revisionable as it is used as @key entity key.', array('@field' => $base_field_definitions[$field_name]->getLabel(), '@key' => $key)));
+    foreach (array_intersect_key($keys, array_flip(['id', 'revision', 'uuid', 'bundle'])) as $key => $field_name) {
+      if (!isset($base_field_definitions[$field_name])) {
+        throw new \LogicException(String::format('The @field field definition does not exist and it is used as @key entity key.', array(
+          '@field' => $base_field_definitions[$field_name]->getLabel(),
+          '@key' => $key
+        )));
       }
-      if (isset($base_field_definitions[$field_name]) && in_array($key, $fixed_keys) && $base_field_definitions[$field_name]->isTranslatable()) {
-        throw new \LogicException(String::format('The @field field cannot be translatable as it is used as @key entity key.', array('@field' => $base_field_definitions[$field_name]->getLabel(), '@key' => $key)));
+      if ($base_field_definitions[$field_name]->isRevisionable()) {
+        throw new \LogicException(String::format('The @field field cannot be revisionable as it is used as @key entity key.', array(
+          '@field' => $base_field_definitions[$field_name]->getLabel(),
+          '@key' => $key
+        )));
+      }
+      if ($base_field_definitions[$field_name]->isTranslatable()) {
+        throw new \LogicException(String::format('The @field field cannot be translatable as it is used as @key entity key.', array(
+          '@field' => $base_field_definitions[$field_name]->getLabel(),
+          '@key' => $key
+        )));
       }
     }
 
diff --git a/core/lib/Drupal/Core/Entity/FieldableEntityInterface.php b/core/lib/Drupal/Core/Entity/FieldableEntityInterface.php
index 5b6af02..08674f2 100644
--- a/core/lib/Drupal/Core/Entity/FieldableEntityInterface.php
+++ b/core/lib/Drupal/Core/Entity/FieldableEntityInterface.php
@@ -193,7 +193,13 @@ public function getFields($include_computed = TRUE);
    * @param string $field_name
    *   The name of the field which is changed.
    *
+   * @throws \InvalidArgumentException
+   *   When trying to assign a value to the language field that matches an
+   *   existing translation.
    * @throws \LogicException
+   *   When trying to change:
+   *   - the language of a translation;
+   *   - the value of the flag identifying the default translation object.
    */
   public function onChange($field_name);