diff --git a/src/ApiClient/Client.php b/src/ApiClient/Client.php
index a82e23a..52238dc 100644
--- a/src/ApiClient/Client.php
+++ b/src/ApiClient/Client.php
@@ -100,7 +100,7 @@ protected function call(string $method, string $path, array $headers = [], $body
      *
      * @throws BokbasenApiClientException
      */
-    public function post(string $path, $body, ?array $headers = [], bool $authenticate = true): ResponseInterface
+    public function post(string $path, $body, array $headers = [], bool $authenticate = true): ResponseInterface
     {
         return $this->call(
             HttpRequestOptions::HTTP_METHOD_POST,