diff --git a/CHANGELOG.md b/CHANGELOG.md
index 84f64cee..8f7d180a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Fixed
 - Fixed a JavaScript error that occurred when pasting a block type
 - Fixed an incorrect German translation of 'Min Blocks' (thanks @alumpe)
+- Fixed a bug where the child blocks UI element wasn't appearing on the field layout designer sidebar on existing block types
 
 ## 3.1.8 - 2022-07-15
 
diff --git a/src/controllers/Configurator.php b/src/controllers/Configurator.php
index 397207aa..17357553 100644
--- a/src/controllers/Configurator.php
+++ b/src/controllers/Configurator.php
@@ -33,9 +33,13 @@ public function actionRenderFieldLayout(): Response
         $config = $request->getBodyParam('layout');
 
         // Prioritise the config
-        $fieldLayout = $config
-            ? FieldLayout::createFromConfig($config)
-            : ($id ? Craft::$app->getFields()->getLayoutById($id) : new FieldLayout(['type' => Block::class]));
+        if ($config) {
+            $fieldLayout = FieldLayout::createFromConfig($config);
+            $fieldLayout->type = Block::class;
+        } else {
+            $fieldLayout = $id ? Craft::$app->getFields()->getLayoutById($id) : new FieldLayout(['type' => Block::class]);
+        }
+
         $html = Neo::$plugin->blockTypes->renderFieldLayoutDesigner($fieldLayout);
 
         return $this->asJson([