diff --git a/src/migrate.ts b/src/migrate.ts
index 614b20cae..18217f408 100644
--- a/src/migrate.ts
+++ b/src/migrate.ts
@@ -24,9 +24,14 @@ import { UserPublickey } from './models/entities/user-publickey';
 import { UserKeypair } from './models/entities/user-keypair';
 import { extractPublic } from './crypto_key';
 import { Emoji } from './models/entities/emoji';
-import { toPuny } from './misc/convert-host';
+import { toPuny as _toPuny } from './misc/convert-host';
 import { UserProfile } from './models/entities/user-profile';
 
+function toPuny(x: string | null): string | null {
+	if (x == null) return null;
+	return _toPuny(x);
+}
+
 const u = (config as any).mongodb.user ? encodeURIComponent((config as any).mongodb.user) : null;
 const p = (config as any).mongodb.pass ? encodeURIComponent((config as any).mongodb.pass) : null;