diff --git a/lib/activitypub/middleware/http-signature.ts b/lib/activitypub/middleware/http-signature.ts
index 4d3e827..4f583b8 100644
--- a/lib/activitypub/middleware/http-signature.ts
+++ b/lib/activitypub/middleware/http-signature.ts
@@ -8,7 +8,7 @@ export = async (req: Request, res: Response, next: NextFunction) => {
 		return;
 	}
 	const actor = await getActor(req.body.actor as string);
-	if (actor && validate(req, actor.publicKey.publicKeyPem)) {
+	if (actor && actor.publicKey && validate(req, actor.publicKey.publicKeyPem)) {
 		next();
 	} else {
 		// if the first check fails, force re-fetch the actor and try again