diff --git a/pyproject.toml b/pyproject.toml
index 8290502..dc4f043 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -105,6 +105,13 @@ convention = "numpy"
 [tool.pytest.ini_options]
 addopts = ["--doctest-modules"]
 asyncio_default_fixture_loop_scope = "function"
+filterwarnings = [
+  # Treat warnings emitted during tests as errors. (This way we can explicitly
+  # ignore warnings we know to be OK.)
+  "error",
+  # Triggered by the fairly old version of protobuf we use
+  'ignore:_SixMetaPathImporter\.find_spec\(\)\ not\ found;\ falling\ back\ to\ find_module\(\):ImportWarning:importlib._bootstrap'
+]
 
 [tool.coverage.run]
 omit = [
diff --git a/test/test_kv.py b/test/test_kv.py
index 67e61cf..83d9a0f 100644
--- a/test/test_kv.py
+++ b/test/test_kv.py
@@ -404,6 +404,23 @@ def db(create_db: partial[Kv]) -> Kv:
     return create_db()
 
 
+@pytest.fixture
+def stopped_loop() -> Generator[asyncio.AbstractEventLoop]:
+    """Get an asyncio loop that is not actively running anything."""
+    try:
+        loop = asyncio.new_event_loop()
+        yield loop
+        assert not loop.is_running()
+    finally:
+
+        async def close() -> None:
+            await asyncio.wait_for(loop.shutdown_asyncgens(), timeout=0.1)
+            await asyncio.wait_for(loop.shutdown_default_executor(), timeout=0.1)
+
+        loop.run_until_complete(close())
+        loop.close()
+
+
 def pack_kv_entry(
     key: AnyKvKey, value: bytes, versionstamp: int = 1
 ) -> ProtobufKvEntry:
@@ -1020,8 +1037,10 @@ def use_kv_and_finalize() -> None:
     assert session.closed
 
 
-def test_close_via_finalizer__loop_not_running() -> None:
-    loop = asyncio.new_event_loop()
+def test_close_via_finalizer__loop_not_running(
+    stopped_loop: asyncio.AbstractEventLoop,
+) -> None:
+    loop = stopped_loop
     authenticator = Mock()
 
     async def create_session() -> aiohttp.ClientSession: