diff --git a/flask_oauthlib/provider/oauth2.py b/flask_oauthlib/provider/oauth2.py
index 2c140945..6b35b8dc 100644
--- a/flask_oauthlib/provider/oauth2.py
+++ b/flask_oauthlib/provider/oauth2.py
@@ -815,7 +815,7 @@ def validate_redirect_uri(self, client_id, redirect_uri, request,
         redirect_uris strictly, you can add a `validate_redirect_uri`
         function on grant for a customized validation.
         """
-        request.client = request.client = self._clientgetter(client_id)
+        request.client = request.client or self._clientgetter(client_id)
         client = request.client
         if hasattr(client, 'validate_redirect_uri'):
             return client.validate_redirect_uri(redirect_uri)