diff --git a/src/remote/activitypub/request.ts b/src/remote/activitypub/request.ts
index 585c1c0ce8..cebce8c48a 100644
--- a/src/remote/activitypub/request.ts
+++ b/src/remote/activitypub/request.ts
@@ -19,6 +19,9 @@ export default (user: ILocalUser, url: string, object: any) => new Promise((reso
 		port,
 		method: 'POST',
 		path: pathname + search,
+		headers: {
+			'Content-Type': 'application/activity+json'
+		}
 	}, res => {
 		log(`${url} --> ${res.statusCode}`);