diff --git a/src/auth/auth.service.ts b/src/auth/auth.service.ts
index aa8966c..2b5a48c 100644
--- a/src/auth/auth.service.ts
+++ b/src/auth/auth.service.ts
@@ -8,6 +8,6 @@
 
   /** Ticket #42 — refresh token rotation (demo change for invalidation). */
   rotateRefreshToken(oldToken: string): string {
-    return `rotated:${oldToken}`;
+    return `rotated:${oldToken}:${Date.now()}`;
   }
 }