diff --git a/src/core/Schemas.ts b/src/core/Schemas.ts
index 1a334b6d0..7e2fff5e2 100644
--- a/src/core/Schemas.ts
+++ b/src/core/Schemas.ts
@@ -430,7 +430,7 @@ export const ClientJoinMessageSchema = z.object({
   gameID: ID,
   lastTurn: z.number(), // The last turn the client saw.
   username: SafeString,
-  flag: SafeString.nullable(),
+  flag: SafeString.optional(),
 });
 
 export const ClientMessageSchema = z.union([
diff --git a/src/server/Client.ts b/src/server/Client.ts
index a3587c3cd..d5fc46e04 100644
--- a/src/server/Client.ts
+++ b/src/server/Client.ts
@@ -18,6 +18,6 @@ export class Client {
     public readonly ip: string,
     public readonly username: string,
     public readonly ws: WebSocket,
-    public readonly flag: string | null,
+    public readonly flag: string | undefined,
   ) {}
 }
diff --git a/src/server/GameServer.ts b/src/server/GameServer.ts
index 4697c73e3..ec9059468 100644
--- a/src/server/GameServer.ts
+++ b/src/server/GameServer.ts
@@ -296,7 +296,7 @@ export class GameServer {
         clientID: c.clientID,
         flag: c.flag,
       })),
-    });
+    } satisfies GameStartInfo);
 
     this.endTurnIntervalID = setInterval(
       () => this.endTurn(),