diff --git a/src/pyop/provider.py b/src/pyop/provider.py
index 67f9c2d..5d01f73 100644
--- a/src/pyop/provider.py
+++ b/src/pyop/provider.py
@@ -446,7 +446,8 @@ def _do_code_exchange(self, request,  # type: Dict[str, str]
         if refresh_token is not None:
             response['refresh_token'] = refresh_token
 
-        extra_id_token_claims = {}
+        extra_id_token_claims = extra_id_token_claims or {}
+
         if self.stateless:
             extra_id_token_claims_in_code = self.authz_state.get_extra_id_token_claims_for_code(token_request['code'])
             extra_id_token_claims.update(extra_id_token_claims_in_code)