diff --git a/src/Model/MailingList/ValidateResponse.php b/src/Model/MailingList/ValidateResponse.php
index 6dc8a48..a86e44e 100644
--- a/src/Model/MailingList/ValidateResponse.php
+++ b/src/Model/MailingList/ValidateResponse.php
@@ -21,8 +21,8 @@ final class ValidateResponse implements ApiResponse
     public static function create(array $data): self
     {
         $model = new self();
-        $model->id = $data['id'] ?? '';
-        $model->message = $data['message'] ?? '';
+        $model->id = $data['id'] ?? null;
+        $model->message = $data['message'] ?? null;
 
         return $model;
     }
@@ -31,12 +31,12 @@ final class ValidateResponse implements ApiResponse
     {
     }
 
-    public function getMessage(): string
+    public function getMessage(): ?string
     {
         return $this->message;
     }
 
-    public function getId(): string
+    public function getId(): ?string
     {
         return $this->id;
     }
diff --git a/src/Model/MailingList/ValidationStatusDownloadUrl.php b/src/Model/MailingList/ValidationStatusDownloadUrl.php
index 60f9958..f66d628 100644
--- a/src/Model/MailingList/ValidationStatusDownloadUrl.php
+++ b/src/Model/MailingList/ValidationStatusDownloadUrl.php
@@ -21,8 +21,8 @@ final class ValidationStatusDownloadUrl implements ApiResponse
     public static function create(array $data): self
     {
         $model = new self();
-        $model->csv = $data['csv'] ?? '';
-        $model->json = $data['json'] ?? '';
+        $model->csv = $data['csv'] ?? null;
+        $model->json = $data['json'] ?? null;
 
         return $model;
     }
@@ -31,12 +31,12 @@ final class ValidationStatusDownloadUrl implements ApiResponse
     {
     }
 
-    public function getCsv(): string
+    public function getCsv(): ?string
     {
         return $this->csv;
     }
 
-    public function getJson(): string
+    public function getJson(): ?string
     {
         return $this->json;
     }
diff --git a/src/Model/MailingList/ValidationStatusResponse.php b/src/Model/MailingList/ValidationStatusResponse.php
index 5f3dc4a..30391f1 100644
--- a/src/Model/MailingList/ValidationStatusResponse.php
+++ b/src/Model/MailingList/ValidationStatusResponse.php
@@ -26,13 +26,13 @@ final class ValidationStatusResponse implements ApiResponse
     public static function create(array $data): self
     {
         $model = new self();
-        $model->id = $data['id'] ?? '';
+        $model->id = $data['id'] ?? null;
         $model->createdAt = $data['created_at'] ?? null;
         $model->downloadUrl = ValidationStatusDownloadUrl::create($data['download_url']);
-        $model->id = $data['id'] ?? '';
+        $model->id = $data['id'] ?? null;
         $model->quantity = $data['quantity'] ?? 0;
-        $model->recordsProcessed = $data['records_processed'] ?? 0;
-        $model->status = $data['status'] ?? '';
+        $model->recordsProcessed = $data['records_processed'] ?? null;
+        $model->status = $data['status'] ?? null;
         $model->summary = ValidationStatusSummary::create($data['summary'] ?? []);
 
         return $model;
@@ -42,7 +42,7 @@ final class ValidationStatusResponse implements ApiResponse
     {
     }
 
-    public function getCreatedAt(): string
+    public function getCreatedAt(): ?string
     {
         return $this->createdAt;
     }
@@ -52,22 +52,22 @@ final class ValidationStatusResponse implements ApiResponse
         return $this->downloadUrl;
     }
 
-    public function getId(): string
+    public function getId(): ?string
     {
         return $this->id;
     }
 
-    public function getQuantity(): int
+    public function getQuantity(): ?int
     {
         return $this->quantity;
     }
 
-    public function getRecordsProcessed(): int
+    public function getRecordsProcessed(): ?int
     {
         return $this->recordsProcessed;
     }
 
-    public function getStatus(): string
+    public function getStatus(): ?string
     {
         return $this->status;
     }