diff --git a/abandonauth/routers/ui.py b/abandonauth/routers/ui.py
index dfce08a..40e8804 100644
--- a/abandonauth/routers/ui.py
+++ b/abandonauth/routers/ui.py
@@ -1,11 +1,12 @@
 from typing import Annotated
+from uuid import UUID
 
 import httpx
 from fastapi import APIRouter, Form, Request, HTTPException
 from fastapi.responses import HTMLResponse, RedirectResponse
 from fastapi.templating import Jinja2Templates
 from prisma.models import DeveloperApplication
-from starlette.status import HTTP_403_FORBIDDEN, HTTP_400_BAD_REQUEST, HTTP_303_SEE_OTHER
+from starlette.status import HTTP_403_FORBIDDEN, HTTP_400_BAD_REQUEST, HTTP_303_SEE_OTHER, HTTP_404_NOT_FOUND
 
 from abandonauth import templates  # type: ignore
 
@@ -319,7 +320,7 @@ async def edit_dev_application_callback_uris(
 
 
 @router.get("/login", response_class=HTMLResponse, include_in_schema=False)
-async def oauth_login(request: Request, application_id: str | None = None, callback_uri: str | None = None):
+async def oauth_login(request: Request, application_id: UUID | None = None, callback_uri: str | None = None):
     """Login for initiating the OAuth flow
 
     This page is used to start the OAuth flow for applications using AbandonAuth.
@@ -335,13 +336,18 @@ async def oauth_login(request: Request, application_id: str | None = None, callb
         )
     else:
         dev_app = await DeveloperApplication.prisma().find_unique(
-            where={"id": application_id},
+            where={"id": str(application_id)},
             include={"callback_uris": True}
         )
 
         # This check is a convenience in order to provide accurate and immediate feedback to users
         # The security check for application IDs and callback URIs must be done later in the auth flow
-        if not dev_app or not dev_app.callback_uris or callback_uri not in [x.uri for x in dev_app.callback_uris]:
+        if not dev_app:
+            raise HTTPException(
+                status_code=HTTP_404_NOT_FOUND,
+                detail="Invalid application ID",
+            )
+        if not dev_app.callback_uris or callback_uri not in [x.uri for x in dev_app.callback_uris]:
             raise HTTPException(
                 status_code=HTTP_403_FORBIDDEN,
                 detail="Invalid application ID or callback_uri",