diff --git a/lib/mastodon/routes/oauth.js b/lib/mastodon/routes/oauth.js
index 2a31c1c..58f6c81 100644
--- a/lib/mastodon/routes/oauth.js
+++ b/lib/mastodon/routes/oauth.js
@@ -610,6 +610,7 @@ router.post("/oauth/token", async (req, res, next) => {
           refreshToken,
           refreshExpiresAt: new Date(Date.now() + REFRESH_TOKEN_TTL),
         },
+        $unset: { expiresAt: "" },
       },
     );