diff --git a/tests/entrypoints/openai/test_basic.py b/tests/entrypoints/openai/test_basic.py
index 2c370b01db6f2..de329d8cc6659 100644
--- a/tests/entrypoints/openai/test_basic.py
+++ b/tests/entrypoints/openai/test_basic.py
@@ -59,6 +59,5 @@ async def test_log_metrics(client: openai.AsyncOpenAI):
     base_url = str(client.base_url)[:-3].strip("/")
 
     response = requests.get(base_url + "/metrics")
-    response.raise_for_status()
 
-    assert response.json() is not None
+    assert response.status_code == HTTPStatus.OK
diff --git a/vllm/entrypoints/openai/api_server.py b/vllm/entrypoints/openai/api_server.py
index 45c634b4a2991..a86a5099d8b8f 100644
--- a/vllm/entrypoints/openai/api_server.py
+++ b/vllm/entrypoints/openai/api_server.py
@@ -70,11 +70,13 @@ async def _force_log():
 
 router = APIRouter()
 
-# Add prometheus asgi middleware to route /metrics requests
-route = Mount("/metrics", make_asgi_app())
-# Workaround for 307 Redirect for /metrics
-route.path_regex = re.compile('^/metrics(?P<path>.*)$')
-router.routes.append(route)
+
+def mount_metrics(app: fastapi.FastAPI):
+    # Add prometheus asgi middleware to route /metrics requests
+    metrics_route = Mount("/metrics", make_asgi_app())
+    # Workaround for 307 Redirect for /metrics
+    metrics_route.path_regex = re.compile('^/metrics(?P<path>.*)$')
+    app.routes.append(metrics_route)
 
 
 @router.get("/health")
@@ -164,6 +166,8 @@ def build_app(args):
     app.include_router(router)
     app.root_path = args.root_path
 
+    mount_metrics(app)
+
     app.add_middleware(
         CORSMiddleware,
         allow_origins=args.allowed_origins,