diff --git a/src/services/userService.ts b/src/services/userService.ts
index 2cc4d44..07798b3 100644
--- a/src/services/userService.ts
+++ b/src/services/userService.ts
@@ -79,6 +79,7 @@ function providerFromToken(token: DecodedIdToken): Provider {
   const raw = token.firebase?.sign_in_provider;
   if (raw === "google.com") return "google";
   if (raw === "apple.com") return "apple";
+  if (raw === "anonymous") return "anonymous";
   throw new HttpError(
     400,
     `unsupported sign-in provider: ${raw}`,
diff --git a/src/types/panit.ts b/src/types/panit.ts
index 165fa70..df080ed 100644
--- a/src/types/panit.ts
+++ b/src/types/panit.ts
@@ -1,7 +1,7 @@
 import type { Timestamp } from "firebase-admin/firestore";
 import type { DateString } from "./dateString";
 
-export type Provider = "google" | "apple";
+export type Provider = "google" | "apple" | "anonymous";
 
 export type DailyJudgment = "perfect" | "success" | "fail" | "skip";