diff --git a/tests/ZttpTest.php b/tests/ZttpTest.php
index <HASH>..<HASH> 100644
--- a/tests/ZttpTest.php
+++ b/tests/ZttpTest.php
@@ -113,6 +113,7 @@ class ZttpTest extends TestCase
         ]);
 
         $this->assertTrue($response->isOk());
+        $this->assertStringStartsWith('multipart', $response->json()['headers']['content-type'][0]);
     }
 
     /** @test */
Adds a content-type assertion to the multi-part request