diff --git a/core/lib/Drupal/Core/Config/TypedConfigManager.php b/core/lib/Drupal/Core/Config/TypedConfigManager.php
index 36ff68b..cad220c 100644
--- a/core/lib/Drupal/Core/Config/TypedConfigManager.php
+++ b/core/lib/Drupal/Core/Config/TypedConfigManager.php
@@ -175,10 +175,11 @@ protected function getDefinitionWithReplacements($base_plugin_id, array $replace
         // definition.
         $definition = NestedArray::mergeDeepArray([$definitions[$sub_type], $definition], TRUE);
       }
-
-      // Unset type so we try the merge only once per type.
-      unset($definition['type']);
-      $this->definitions[$type] = $definition;
+      else {
+        // Unset type so we try the merge only once per type.
+        unset($definition['type']);
+        $this->definitions[$type] = $definition;
+      }
     }
     // Add type and default definition class.
     $definition += array(