diff --git a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
index 9b04e9c..b127a229 100644
--- a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
+++ b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
@@ -443,6 +443,12 @@ public function setDefaultValueCallback($callback) {
    * @return $this
    */
   public function setDefaultValue($value) {
+    if (!is_array($value)) {
+      $value = array(array($this->getMainPropertyName() => $value));
+    }
+    elseif (!is_numeric(array_keys($value)[0])) {
+      $value = array(0 => $value);
+    }
     $this->definition['default_value'] = $value;
     return $this;
   }
diff --git a/core/modules/content_translation/config/schema/content_translation.schema.yml b/core/modules/content_translation/config/schema/content_translation.schema.yml
index db56a16..a4bc176 100644
--- a/core/modules/content_translation/config/schema/content_translation.schema.yml
+++ b/core/modules/content_translation/config/schema/content_translation.schema.yml
@@ -7,6 +7,7 @@ content_translation.settings:
   sequence:
     - type: sequence
       label: 'Bundle'
+      sequence:
         - type: mapping
           label: 'Settings'
           mapping:
diff --git a/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php b/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
index bc88b21..ae71170 100644
--- a/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/BaseFieldDefinitionTest.php
@@ -164,6 +164,7 @@ public function testFieldDefaultValue() {
     $default_value = array(
       'value' => $this->randomMachineName(),
     );
+    $expected_default_value = array($default_value);
     $definition->setDefaultValue($default_value);
     $entity = $this->getMockBuilder('Drupal\Core\Entity\ContentEntityBase')
       ->disableOriginalConstructor()
@@ -171,7 +172,23 @@ public function testFieldDefaultValue() {
     // Set the field item list class to be used to avoid requiring the typed
     // data manager to retrieve it.
     $definition->setClass('Drupal\Core\Field\FieldItemList');
-    $this->assertEquals($default_value, $definition->getDefaultValue($entity));
+    $this->assertEquals($expected_default_value, $definition->getDefaultValue($entity));
+
+    $data_definition = $this->getMockBuilder('Drupal\Core\TypedData\DataDefinition')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $data_definition->expects($this->any())
+      ->method('getClass')
+      ->will($this->returnValue('Drupal\Core\Field\FieldItemBase'));
+    $definition->setItemDefinition($data_definition);
+
+    // Set default value only with a literal.
+    $definition->setDefaultValue($default_value['value']);
+    $this->assertEquals($expected_default_value, $definition->getDefaultValue($entity));
+
+    // Set default value with an indexed array.
+    $definition->setDefaultValue($expected_default_value);
+    $this->assertEquals($expected_default_value, $definition->getDefaultValue($entity));
   }
 
   /**