diff --git a/pyproject.toml b/pyproject.toml
index 7a2e796..9b410aa 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,7 +55,7 @@ requires = ["setuptools"]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools]
-packages = ["daphne"]
+package-dir = { daphne = "daphne", twisted = "daphne/twisted" }
 
 [tool.setuptools.dynamic]
 version = { attr = "daphne.__version__" }
diff --git a/tests/test_packaging.py b/tests/test_packaging.py
new file mode 100644
index 0000000..2107b5d
--- /dev/null
+++ b/tests/test_packaging.py
@@ -0,0 +1,15 @@
+import sys
+from pathlib import Path
+
+
+def test_fd_endpoint_plugin_installed():
+    # Find the site-packages directory
+    for path in sys.path:
+        if "site-packages" in path:
+            site_packages = Path(path)
+            break
+    else:
+        raise AssertionError("Could not find site-packages in sys.path")
+
+    plugin_path = site_packages / "twisted" / "plugins" / "fd_endpoint.py"
+    assert plugin_path.exists(), f"fd_endpoint.py not found at {plugin_path}"