diff --git a/lite_bootstrap/helpers/fastapi_helpers.py b/lite_bootstrap/helpers/fastapi_helpers.py
index 76518de..62804cc 100644
--- a/lite_bootstrap/helpers/fastapi_helpers.py
+++ b/lite_bootstrap/helpers/fastapi_helpers.py
@@ -1,5 +1,4 @@
 import pathlib
-import typing
 import warnings
 
 from lite_bootstrap import import_checker
@@ -47,10 +46,13 @@ def enable_offline_docs(
     redoc_url: str = app.redoc_url or "/redoc"
     swagger_ui_oauth2_redirect_url: str = app.swagger_ui_oauth2_redirect_url or "/docs/oauth2-redirect"
 
+    replaced_urls = (docs_url, redoc_url, swagger_ui_oauth2_redirect_url)
     app.router.routes = [
         route
         for route in app.router.routes
-        if typing.cast(Route, route).path not in (docs_url, redoc_url, swagger_ui_oauth2_redirect_url)
+        # Only the auto-generated docs endpoints are plain ``Route``s with a ``path``; other route
+        # types (e.g. FastAPI's ``_IncludedRouter``) lack ``.path`` and must be left untouched.
+        if not (isinstance(route, Route) and route.path in replaced_urls)
     ]
 
     static_dir_path = pathlib.Path(__file__).parent.parent / "static/fastapi_docs"
diff --git a/pyproject.toml b/pyproject.toml
index 6f03f31..82dd146 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -58,7 +58,11 @@ free-all = [
     "lite-bootstrap[sentry,otl,logging,pyroscope]",
 ]
 fastapi = [
-    "fastapi",
+    # FastAPI 0.137 introduced the internal `_IncludedRouter` route type, which
+    # prometheus-fastapi-instrumentator (<=8.0.0) does not handle (it reads `route.path`
+    # unconditionally and raises AttributeError). Cap until a fixed instrumentator ships.
+    # Upstream issue: https://github.com/trallnag/prometheus-fastapi-instrumentator/issues/370
+    "fastapi<0.137",
 ]
 fastapi-sentry = [
     "lite-bootstrap[fastapi,sentry]",