diff --git a/lib/Controller/AttachmentApiController.php b/lib/Controller/AttachmentApiController.php
index d8a35db59..b50e7d9f9 100644
--- a/lib/Controller/AttachmentApiController.php
+++ b/lib/Controller/AttachmentApiController.php
@@ -48,7 +48,7 @@ public function display(int $cardId, int $attachmentId, string $type = 'deck_fil
 	#[CORS]
 	#[NoCSRFRequired]
 	public function create(int $cardId, string $type, ?string $data): DataResponse {
-		$attachment = $this->attachmentService->create($cardId, $type, $data);
+		$attachment = $this->attachmentService->create($cardId, $type, $data ?? '');
 		return new DataResponse($attachment, HTTP::STATUS_OK);
 	}