diff --git a/backend/open_webui/config.py b/backend/open_webui/config.py
index 2c780a330..6ece5e71e 100644
--- a/backend/open_webui/config.py
+++ b/backend/open_webui/config.py
@@ -815,10 +815,13 @@ def load_oauth_providers():
     # Always register Letta OAuth provider (this is a Letta-focused deployment)
     def letta_oauth_register(oauth: OAuth):
         # Letta returns token_type: "access_token" instead of "Bearer", fix it
-        def letta_compliance_fix(client, token):
-            if token.get("token_type") == "access_token":
-                token["token_type"] = "Bearer"
-            return token
+        def letta_compliance_fix(session):
+            def _fix_token_response(response):
+                data = response.json()
+                if data.get("token_type") == "access_token":
+                    data["token_type"] = "Bearer"
+                return data
+            session.register_compliance_hook("access_token_response", _fix_token_response)
 
         client = oauth.register(
             name="letta",