diff --git a/lib/Controller/AttachmentApiController.php b/lib/Controller/AttachmentApiController.php
index 7ece834331..d8a35db59b 100644
--- a/lib/Controller/AttachmentApiController.php
+++ b/lib/Controller/AttachmentApiController.php
@@ -47,7 +47,7 @@ public function display(int $cardId, int $attachmentId, string $type = 'deck_fil
 	#[NoAdminRequired]
 	#[CORS]
 	#[NoCSRFRequired]
-	public function create(int $cardId, string $type, string $data): DataResponse {
+	public function create(int $cardId, string $type, ?string $data): DataResponse {
 		$attachment = $this->attachmentService->create($cardId, $type, $data);
 		return new DataResponse($attachment, HTTP::STATUS_OK);
 	}