diff --git a/src/server/Client.ts b/src/server/Client.ts
index 6d39347e9..1a5d645cf 100644
--- a/src/server/Client.ts
+++ b/src/server/Client.ts
@@ -19,6 +19,6 @@ export class Client {
     public readonly username: string,
     public readonly ws: WebSocket,
     public readonly flag: string | null,
-    public readonly pattern: string | null,
+    public readonly pattern: string | undefined | null,
   ) {}
 }