diff --git a/lib/client.js b/lib/client.js
index <HASH>..<HASH> 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -603,6 +603,7 @@ class Client {
   grant(body) {
     assert(this.issuer.token_endpoint, 'issuer must be configured with token endpoint');
     return this.authenticatedPost('token', { body: _.omitBy(body, _.isUndefined) })
+      .then(expectResponse(200))
       .then(response => new TokenSet(JSON.parse(response.body)));
   }
expectResponse <I> on grant calls