diff --git a/tests/test_health.py b/tests/test_health.py
index 79c973b..a19ab73 100644
--- a/tests/test_health.py
+++ b/tests/test_health.py
@@ -1,7 +1,41 @@
 from __future__ import annotations
 
+from sqlalchemy.exc import OperationalError
+
+from quartermaster.db import get_session
+from quartermaster.main import create_app
+from fastapi.testclient import TestClient
+
 
 def test_healthz_returns_ok(client):
     response = client.get("/healthz")
     assert response.status_code == 200
     assert response.json() == {"status": "ok"}
+
+
+def test_healthz_returns_503_when_db_check_raises():
+    app = create_app()
+
+    def broken_session():
+        class BrokenSession:
+            def execute(self, *args, **kwargs):
+                raise OperationalError("boom", None, Exception("boom"))
+
+            def close(self):
+                pass
+
+        session = BrokenSession()
+        try:
+            yield session
+        finally:
+            session.close()
+
+    app.dependency_overrides[get_session] = broken_session
+
+    with TestClient(app) as client:
+        response = client.get("/healthz")
+
+    assert response.status_code == 503
+    body = response.json()
+    assert body["status"] == "error"
+    assert body["detail"] == "OperationalError"