diff --git a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
index b3e23ae..a466b2a 100644
--- a/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
+++ b/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php
@@ -91,16 +91,7 @@
    * Overrides Entity::__construct().
    */
   public function __construct(array $values, $entity_type) {
-    $this->entityTypeId = $entity_type;
-    // If needed, map the config keys to entity properties.
-    $config_mapping = $this->getEntityType()->getConfigMapping();
-    foreach ($values as $key => $value) {
-      // Check for a config mapping, otherwise use the default key.
-      if (isset($config_mapping[$key])) {
-        $key = $config_mapping[$key];
-      }
-      $this->$key = $value;
-    }
+    parent::__construct($values, $entity_type);
 
     // Backup the original ID, if any.
     // Configuration entity IDs are strings, and '0' is a valid ID.
@@ -260,17 +251,14 @@ public function toArray() {
     $id_key = $this->getEntityType()->getKey('id');
     $config_mapping = $this->getEntityType()->getConfigMapping();
     foreach (array_keys($definition['mapping']) as $name) {
-      // Check for a config mapping, otherwise use the default name.
-      if (isset($config_mapping[$name])) {
-        $name = $config_mapping[$name];
-      }
       // Special handling for IDs so that computed compound IDs work.
       // @see \Drupal\Core\Entity\EntityDisplayBase::id()
       if ($name == $id_key) {
         $properties[$name] = $this->id();
       }
       else {
-        $properties[$name] = $this->get($name);
+        $property_name = isset($config_mapping[$name]) ? $config_mapping[$name] : $name;
+        $properties[$name] = $this->get($property_name);
       }
     }
     return $properties;
@@ -288,6 +276,21 @@ protected function getTypedConfig() {
   /**
    * {@inheritdoc}
    */
+  public static function preCreate(EntityStorageInterface $storage, array &$values) {
+    // If needed, map the config keys to entity properties.
+    $config_mapping = $storage->getEntityType()->getConfigMapping();
+    foreach ($values as $key => $value) {
+      if (isset($config_mapping[$key])) {
+        $new_key = $config_mapping[$key];
+        $values[$new_key] = $value;
+        unset($values[$key]);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function preSave(EntityStorageInterface $storage) {
     parent::preSave($storage);
 
diff --git a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
index 5feb644..d5d03d8 100644
--- a/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityBaseUnitTest.php
@@ -478,6 +478,7 @@ public function testToArrayFallback() {
   }
 
   /**
+   * @covers ::preCreate
    * @covers ::toArray
    */
   public function testToArrayConfigMapping() {
@@ -487,10 +488,22 @@ public function testToArrayConfigMapping() {
     $this->entityType->expects($this->atLeastOnce())
       ->method('getConfigMapping')
       ->willReturn(['foo_bar' => 'fooBar']);
-    $entity = $this->setUpEntity(['foo_bar' => 5]);
-    $properties = $this->entity->toArray();
+    $storage = $this->getMock('\Drupal\Core\Config\Entity\ConfigEntityStorageInterface');
+    $storage->expects($this->any())
+      ->method('getEntityType')
+      ->will($this->returnValue($this->entityType));
+
+    // Confirm that preCreate() maps the values as expected.
+    $values = ['foo_bar' => 5];
+    $entity_class = get_class($this->entity);
+    $entity_class::preCreate($storage, $values);
+    $this->assertEquals(['fooBar' => 5], $values);
+
+    // Confirm that toArray() maps the properties back to config keys.
+    $this->entity = $this->setUpEntity($values);
+    $properties = $this->entity->toArray(true);
     $this->assertInternalType('array', $properties);
-    $this->assertEquals(['id' => $entity->id(), 'dependencies' => [], 'fooBar' => 5], $properties);
+    $this->assertEquals(['id' => $this->entity->id(), 'dependencies' => [], 'foo_bar' => 5], $properties);
   }
 
 }