diff --git a/oauthenticator/oauth2.py b/oauthenticator/oauth2.py
index 00c2aab7..9ac5416c 100644
--- a/oauthenticator/oauth2.py
+++ b/oauthenticator/oauth2.py
@@ -1018,7 +1018,7 @@ def build_refresh_token_request_params(self, refresh_token):
         # the client_id and client_secret should not be included in the access token request params
         # when basic authentication is used
         # ref: https://www.rfc-editor.org/rfc/rfc6749#section-2.3.1
-        if self.basic_auth:
+        if not self.basic_auth:
             params.update(
                 [("client_id", self.client_id), ("client_secret", self.client_secret)]
             )