diff --git a/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
index 5c7aeeb..6ccf8fd 100644
--- a/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -107,9 +107,13 @@ public function buildDataDefinition(array $definition, $value, $name = NULL, $pa
       // Remove the type from the definition so that it is replaced with the
       // concrete type from schema definitions.
       unset($definition['type']);
+
+      $definition += $this->getDefinition($type, TRUE, $replace);
+    }
+    else {
+      // Add default values from type definition.
+      $definition += $this->getDefinition($type);
     }
-    // Add default values from type definition.
-    $definition += $this->getDefinition($type);
 
     $data_definition = $this->createDataDefinition($definition['type']);
 
@@ -125,7 +129,7 @@ public function buildDataDefinition(array $definition, $value, $name = NULL, $pa
   /**
    * {@inheritdoc}
    */
-  public function getDefinition($base_plugin_id, $exception_on_invalid = TRUE) {
+  public function getDefinition($base_plugin_id, $exception_on_invalid = TRUE, $value = NULL) {
     $definitions = $this->getDefinitions();
     if (isset($definitions[$base_plugin_id])) {
       $type = $base_plugin_id;
@@ -145,6 +149,14 @@ public function getDefinition($base_plugin_id, $exception_on_invalid = TRUE) {
       // Preserve integer keys on merge, so sequence item types can override
       // parent settings as opposed to adding unused second, third, etc. items.
       $definition = NestedArray::mergeDeepArray(array($merge, $definition), TRUE);
+
+      // If the sub type has a bracket then lets look that up as well.
+      if (isset($value) && strpos($definition['type'], ']')) {
+        $sub_type = $this->replaceName($definition['type'], $value);
+        $merge = $definitions[$sub_type];
+        $definition = NestedArray::mergeDeepArray(array($merge, $definition), TRUE);
+      }
+
       // Unset type so we try the merge only once per type.
       unset($definition['type']);
       $this->definitions[$type] = $definition;