diff --git a/oauthenticator/oauth2.py b/oauthenticator/oauth2.py
index 70ebb72d..0bc01a23 100644
--- a/oauthenticator/oauth2.py
+++ b/oauthenticator/oauth2.py
@@ -703,7 +703,7 @@ def _client_secret_default(self):
         If the `expires_in` field is  omitted in the OAuth 2.0 token response
         then this value will be the default expiration, in seconds, of the
         access token.
-        """
+        """,
     )
 
     validate_server_cert_env = "OAUTH_TLS_VERIFY"