diff --git a/oauth2client/client.py b/oauth2client/client.py
index 6b580a0..4e8e616 100644
--- a/oauth2client/client.py
+++ b/oauth2client/client.py
@@ -925,7 +925,7 @@
           defaults to Google's endpoints but any OAuth 2.0 provider can be used.
         revoke_uri: string, URI for revoke endpoint.
         kwargs: kwargs, Additional parameters to add to the JWT token, for
-          example prn=joe@xample.org."""
+          example sub=joe@xample.org."""
 
       super(SignedJwtAssertionCredentials, self).__init__(
           None,