diff --git a/buildbot_nix/__init__.py b/buildbot_nix/__init__.py
index 016ca40..06fffe1 100644
--- a/buildbot_nix/__init__.py
+++ b/buildbot_nix/__init__.py
@@ -287,7 +287,7 @@ class ReloadGithubProjects(steps.BuildStep):
 
     @defer.inlineCallbacks
     def run(self) -> Generator[Any, object, Any]:
-        d = threads.deferToThread(self.reload_projects)
+        d = threads.deferToThread(self.reload_projects)  # type: ignore[no-untyped-call]
 
         self.error_msg = ""
 
@@ -677,7 +677,7 @@ class AnyProjectEndpointMatcher(EndpointMatcherBase):
         endpoint_object: Any,
         endpoint_dict: dict[str, Any],
         object_type: str,
-    ) -> Generator[Any, Any, Any]:
+    ) -> Generator[defer.Deferred[Match], Any, Any]:
         res = yield endpoint_object.get({}, endpoint_dict)
         if res is None:
             return None
@@ -704,7 +704,7 @@ class AnyProjectEndpointMatcher(EndpointMatcherBase):
         epobject: Any,
         epdict: dict[str, Any],
         options: dict[str, Any],
-    ) -> Generator[Any, Any, Any]:
+    ) -> defer.Deferred[Match]:
         return self.check_builder(epobject, epdict, "build")
 
     def match_BuildEndpoint_stop(  # noqa: N802
@@ -712,7 +712,7 @@ class AnyProjectEndpointMatcher(EndpointMatcherBase):
         epobject: Any,
         epdict: dict[str, Any],
         options: dict[str, Any],
-    ) -> Generator[Any, Any, Any]:
+    ) -> defer.Deferred[Match]:
         return self.check_builder(epobject, epdict, "build")
 
     def match_BuildRequestEndpoint_stop(  # noqa: N802
@@ -720,7 +720,7 @@ class AnyProjectEndpointMatcher(EndpointMatcherBase):
         epobject: Any,
         epdict: dict[str, Any],
         options: dict[str, Any],
-    ) -> Generator[Any, Any, Any]:
+    ) -> defer.Deferred[Match]:
         return self.check_builder(epobject, epdict, "buildrequest")
 
 
diff --git a/buildbot_nix/worker.py b/buildbot_nix/worker.py
index 749d2aa..3f7139d 100644
--- a/buildbot_nix/worker.py
+++ b/buildbot_nix/worker.py
@@ -6,6 +6,7 @@ from pathlib import Path
 
 from buildbot_worker.bot import Worker
 from twisted.application import service
+from twisted.python import components
 
 
 def require_env(key: str) -> str:
@@ -31,7 +32,7 @@ class WorkerConfig:
 
 
 def setup_worker(
-    application: service.Application,
+    application: components.Componentized,
     builder_id: int,
     config: WorkerConfig,
 ) -> None:
@@ -64,12 +65,12 @@ def setup_worker(
     s.setServiceParent(application)
 
 
-def setup_workers(application: service.Application, config: WorkerConfig) -> None:
+def setup_workers(application: components.Componentized, config: WorkerConfig) -> None:
     for i in range(config.worker_count):
         setup_worker(application, i, config)
 
 
 # note: this line is matched against to check that this is a worker
 # directory; do not edit it.
-application = service.Application("buildbot-worker")
+application = service.Application("buildbot-worker")  # type: ignore[no-untyped-call]
 setup_workers(application, WorkerConfig())
diff --git a/nix/treefmt/flake-module.nix b/nix/treefmt/flake-module.nix
index 258a0e7..4aef50e 100644
--- a/nix/treefmt/flake-module.nix
+++ b/nix/treefmt/flake-module.nix
@@ -10,8 +10,12 @@
       programs.deno.enable = true;
       settings.formatter.shellcheck.options = [ "-s" "bash" ];
 
-      programs.mypy.enable = true;
-      programs.mypy.directories."." = { };
+      programs.mypy = {
+        enable = true;
+        directories.".".extraPythonPackages = [
+          pkgs.python3.pkgs.twisted
+        ];
+      };
       settings.formatter.python = {
         command = "sh";
         options = [
diff --git a/pyproject.toml b/pyproject.toml
index 727cfef..8ceda80 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -100,7 +100,3 @@ ignore_missing_imports = true
 [[tool.mypy.overrides]]
 module = "buildbot_worker.*"
 ignore_missing_imports = true
-
-[[tool.mypy.overrides]]
-module = "twisted.*"
-ignore_missing_imports = true