diff --git a/framework/hosting/simple_module_hosting/_error_handlers.py b/framework/hosting/simple_module_hosting/_error_handlers.py
index 6e2092ee..cf861a77 100644
--- a/framework/hosting/simple_module_hosting/_error_handlers.py
+++ b/framework/hosting/simple_module_hosting/_error_handlers.py
@@ -4,6 +4,8 @@
 
 import logging
 
+from fastapi.encoders import jsonable_encoder
+from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse
 from inertia import (
     Inertia,
@@ -49,6 +51,18 @@ async def not_found_error_handler(request: Request, exc: NotFoundError) -> Respo
     return await render_error_page(request, 404, str(exc))
 
 
+async def request_validation_error_handler(
+    request: Request, exc: RequestValidationError
+) -> Response:
+    """Return an Inertia error page for browser requests with invalid params."""
+    accept = request.headers.get("accept", "")
+    if "text/html" in accept:
+        return await render_error_page(
+            request, 422, "The requested URL contains invalid parameters."
+        )
+    return JSONResponse(status_code=422, content={"detail": jsonable_encoder(exc.errors())})
+
+
 async def unhandled_exception_handler(request: Request, exc: Exception) -> Response:
     logger.exception("Unhandled exception: %s", exc)
     return await render_error_page(request, 500, "")
diff --git a/framework/hosting/simple_module_hosting/_phase_helpers.py b/framework/hosting/simple_module_hosting/_phase_helpers.py
index 743c3440..888337a5 100644
--- a/framework/hosting/simple_module_hosting/_phase_helpers.py
+++ b/framework/hosting/simple_module_hosting/_phase_helpers.py
@@ -12,6 +12,7 @@
 from typing import TYPE_CHECKING
 
 from fastapi import APIRouter, FastAPI
+from fastapi.exceptions import RequestValidationError
 from fastapi.routing import APIRoute
 from fastapi.staticfiles import StaticFiles
 from inertia import (
@@ -26,6 +27,7 @@
 from simple_module_hosting._error_handlers import (
     http_exception_handler,
     not_found_error_handler,
+    request_validation_error_handler,
     unhandled_exception_handler,
 )
 from simple_module_hosting.i18n_middleware import LocaleMiddleware
@@ -53,6 +55,7 @@ def register_exception_handlers(app: FastAPI, modules: list) -> None:
     )
     app.add_exception_handler(HTTPException, http_exception_handler)
     app.add_exception_handler(NotFoundError, not_found_error_handler)
+    app.add_exception_handler(RequestValidationError, request_validation_error_handler)
     app.add_exception_handler(Exception, unhandled_exception_handler)
     for mod in modules:
         mod.register_exception_handlers(app)