diff --git a/core/lib/Drupal/Core/Entity/ContentEntityType.php b/core/lib/Drupal/Core/Entity/ContentEntityType.php
index 322c208917..42b2faab2d 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityType.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityType.php
@@ -87,7 +87,7 @@ public function getRevisionMetadataKeys($include_backwards_compatibility_field_n
         $this->revision_metadata_keys['revision_default'] = 'revision_default';
       }
     }
-    return $this->revision_metadata_keys;
+    return $this->revision_metadata_keys + ['revision_default' => 'revision_default'];
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Entity/EntityFieldManager.php b/core/lib/Drupal/Core/Entity/EntityFieldManager.php
index 4ac7c64c68..9afafd9ae8 100644
--- a/core/lib/Drupal/Core/Entity/EntityFieldManager.php
+++ b/core/lib/Drupal/Core/Entity/EntityFieldManager.php
@@ -227,7 +227,7 @@ protected function buildBaseFieldDefinitions($entity_type_id) {
       // Disable the BC layer to prevent a recursion if the entity type
       // annotation doesn't define the revision metadata keys.
       $revision_metadata_keys_no_bc = $entity_type->getRevisionMetadataKeys(FALSE);
-      $field_name = isset($revision_metadata_keys_no_bc['revision_default']) ? $revision_metadata_keys_no_bc['revision_default'] : 'revision_default';
+      $field_name = $revision_metadata_keys_no_bc['revision_default'];
       $base_field_definitions[$field_name] = BaseFieldDefinition::create('boolean')
         ->setLabel($this->t('Default revision'))
         ->setDescription($this->t('A flag indicating whether this was a default revision when it was saved.'))
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
index c455890dbf..2d3edfc6d4 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchemaConverter.php
@@ -245,7 +245,7 @@ protected function copyData(array &$sandbox) {
     $original_base_table = $original_entity_type->getBaseTable();
 
     $revision_id_key = $temporary_entity_type->getKey('revision');
-    $revision_default_key = $temporary_entity_type->hasRevisionMetadataKey('revision_default') ? $temporary_entity_type->getRevisionMetadataKey('revision_default') : 'revision_default';
+    $revision_default_key = $temporary_entity_type->getRevisionMetadataKey('revision_default');
     $revision_translation_affected_key = $temporary_entity_type->getKey('revision_translation_affected');
 
     // If 'progress' is not set, then this will be the first run of the batch.
@@ -386,7 +386,7 @@ protected function updateFieldStorageDefinitionsToRevisionable(ContentEntityType
     $updated_storage_definitions[$entity_type->getKey('revision')] = $revision_field;
 
     // Add the default revision flag field.
-    $field_name = $entity_type->hasRevisionMetadataKey('revision_default') ? $entity_type->getRevisionMetadataKey('revision_default') : 'revision_default';
+    $field_name = $entity_type->getRevisionMetadataKey('revision_default');
     $storage_definition = BaseFieldDefinition::create('boolean')
       ->setName($field_name)
       ->setTargetEntityTypeId($entity_type->id())
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 4010aae1c7..0fd4b26bdc 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -2078,7 +2078,7 @@ function system_update_8501() {
 
   // Install the 'revision_default' field.
   foreach ($definitions as $entity_type_id => $entity_type) {
-    $field_name = $entity_type->hasRevisionMetadataKey('revision_default') ? $entity_type->getRevisionMetadataKey('revision_default') : 'revision_default';
+    $field_name = $entity_type->getRevisionMetadataKey('revision_default');
     // Install the 'revision_default' field if needed.
     if (!$definition_update_manager->getFieldStorageDefinition($field_name, $entity_type_id)) {
       // Make sure the new "revision_default" revision metadata key is available