diff --git a/src/Transformers/RestfulTransformer.php b/src/Transformers/RestfulTransformer.php
index d60dd3f..3ccb7bb 100644
--- a/src/Transformers/RestfulTransformer.php
+++ b/src/Transformers/RestfulTransformer.php
@@ -123,7 +123,7 @@ protected function transformKeysCase(array $transformed)
         /*
          * However, if the level is 1, we also want to transform the first level of keys in a json field which has been cast to array
          */
-        if ($levels == 1) {
+        if ($levels == 1 && ! is_null($this->model)) {
             foreach ($this->model->getCasts() as $fieldName => $castType) {
                 if ($castType == 'array') {
                     $fieldNameFormatted = $this->formatKeyCase($fieldName);