diff --git a/src/Abstracts/Transformers/Transformer.php b/src/Abstracts/Transformers/Transformer.php
index d7ac7e62..2483f53a 100644
--- a/src/Abstracts/Transformers/Transformer.php
+++ b/src/Abstracts/Transformers/Transformer.php
@@ -2,6 +2,7 @@
 
 namespace Apiato\Core\Abstracts\Transformers;
 
+use Apiato\Core\Contracts\HasResourceKey;
 use Apiato\Core\Exceptions\CoreInternalErrorException;
 use Apiato\Core\Exceptions\UnsupportedFractalIncludeException;
 use Illuminate\Support\Facades\Config;
@@ -13,30 +14,31 @@
 
 abstract class Transformer extends FractalTransformer
 {
-    public function nullableItem($data, $transformer, $resourceKey = null): Primitive|Item
+    protected function nullableItem($data, $transformer, $resourceKey = null): Primitive|Item
     {
         if (is_null($data)) {
             return $this->primitive(null);
         }
 
-        return $this->item($data, $transformer, $resourceKey = null);
+        return $this->item($data, $transformer, $resourceKey);
     }
 
-    public function item($data, $transformer, $resourceKey = null): Item
+    protected function item($data, $transformer, string|null $resourceKey = null): Item
     {
-        // set a default resource key if none is set
-        if (!$resourceKey && $data) {
+        if (!$resourceKey && $data instanceof HasResourceKey) {
             $resourceKey = $data->getResourceKey();
         }
 
         return parent::item($data, $transformer, $resourceKey);
     }
 
-    public function collection($data, $transformer, $resourceKey = null): Collection
+    protected function collection($data, $transformer, string|null $resourceKey = null): Collection
     {
-        // set a default resource key if none is set
         if (!$resourceKey && $data->isNotEmpty()) {
-            $resourceKey = $data->first()->getResourceKey();
+            $firstItem = $data->first();
+            if ($firstItem instanceof HasResourceKey) {
+                $resourceKey = $firstItem->getResourceKey();
+            }
         }
 
         return parent::collection($data, $transformer, $resourceKey);