diff --git a/quart_session/sessions.py b/quart_session/sessions.py
index 90a25e2..fa52faf 100644
--- a/quart_session/sessions.py
+++ b/quart_session/sessions.py
@@ -229,7 +229,7 @@ class RedisSessionInterface(SessionInterface):
         """
         if self.backend is None:
             import aioredis
-            uri = app.config.get('SESSION_URI', 'redis://localhost')
+            uri = self._config.get('SESSION_URI', 'redis://localhost')
             self.backend = await aioredis.from_url(
                 uri, encoding="utf-8", decode_responses=True
             )