diff --git a/starlette/staticfiles.py b/starlette/staticfiles.py
index 07cafe5a..38cc7b68 100644
--- a/starlette/staticfiles.py
+++ b/starlette/staticfiles.py
@@ -1,25 +1,28 @@
-from starlette.responses import PlainTextResponse, FileResponse
-from aiofiles.os import stat as aio_stat
 import os
 import stat
 
+from aiofiles.os import stat as aio_stat
+
+from starlette.responses import PlainTextResponse, FileResponse, Response
+from starlette.types import Send, Receive, Scope, ASGIInstance
+
 
 class StaticFile:
-    def __init__(self, *, path):
+    def __init__(self, *, path: str) -> None:
         self.path = path
 
-    def __call__(self, scope):
+    def __call__(self, scope: Scope) -> ASGIInstance:
         if scope["method"] not in ("GET", "HEAD"):
             return PlainTextResponse("Method Not Allowed", status_code=405)
         return _StaticFileResponder(scope, path=self.path)
 
 
 class StaticFiles:
-    def __init__(self, *, directory):
+    def __init__(self, *, directory: str) -> None:
         self.directory = directory
         self.config_checked = False
 
-    def __call__(self, scope):
+    def __call__(self, scope: Scope) -> ASGIInstance:
         if scope["method"] not in ("GET", "HEAD"):
             return PlainTextResponse("Method Not Allowed", status_code=405)
         path = os.path.normpath(os.path.join(*scope["path"].split("/")))
@@ -35,11 +38,11 @@ class StaticFiles:
 
 
 class _StaticFileResponder:
-    def __init__(self, scope, path):
+    def __init__(self, scope: Scope, path: str) -> None:
         self.scope = scope
         self.path = path
 
-    async def __call__(self, receive, send):
+    async def __call__(self, receive: Receive, send: Send) -> None:
         try:
             stat_result = await aio_stat(self.path)
         except FileNotFoundError:
@@ -54,12 +57,12 @@ class _StaticFileResponder:
 
 
 class _StaticFilesResponder:
-    def __init__(self, scope, path, check_directory=None):
+    def __init__(self, scope: Scope, path: str, check_directory: str = None) -> None:
         self.scope = scope
         self.path = path
         self.check_directory = check_directory
 
-    async def check_directory_configured_correctly(self):
+    async def check_directory_configured_correctly(self) -> None:
         """
         Perform a one-off configuration check that StaticFiles is actually
         pointed at a directory, so that we can raise loud errors rather than
@@ -73,14 +76,14 @@ class _StaticFilesResponder:
         if not (stat.S_ISDIR(stat_result.st_mode) or stat.S_ISLNK(stat_result.st_mode)):
             raise RuntimeError("StaticFiles path '%s' is not a directory." % directory)
 
-    async def __call__(self, receive, send):
+    async def __call__(self, receive: Receive, send: Send) -> None:
         if self.check_directory is not None:
             await self.check_directory_configured_correctly()
 
         try:
             stat_result = await aio_stat(self.path)
         except FileNotFoundError:
-            response = PlainTextResponse("Not Found", status_code=404)
+            response = PlainTextResponse("Not Found", status_code=404)  # type: Response
         else:
             mode = stat_result.st_mode
             if not stat.S_ISREG(mode):
diff --git a/tests/test_staticfiles.py b/tests/test_staticfiles.py
index c5a2a66f..74bdc57d 100644
--- a/tests/test_staticfiles.py
+++ b/tests/test_staticfiles.py
@@ -1,8 +1,9 @@
-from starlette.testclient import TestClient
-from starlette.staticfiles import StaticFile, StaticFiles
 import os
 import pytest
 
+from starlette.testclient import TestClient
+from starlette.staticfiles import StaticFile, StaticFiles
+
 
 def test_staticfile(tmpdir):
     path = os.path.join(tmpdir, "example.txt")
@@ -47,7 +48,7 @@ def test_staticfile_with_directory_raises_error(tmpdir):
     app = StaticFile(path=tmpdir)
     client = TestClient(app)
     with pytest.raises(RuntimeError) as exc:
-        response = client.get("/")
+        client.get("/")
     assert "is not a file" in str(exc)
 
 
@@ -56,7 +57,7 @@ def test_staticfile_with_missing_file_raises_error(tmpdir):
     app = StaticFile(path=path)
     client = TestClient(app)
     with pytest.raises(RuntimeError) as exc:
-        response = client.get("/")
+        client.get("/")
     assert "does not exist" in str(exc)
 
 
@@ -113,7 +114,7 @@ def test_staticfiles_configured_with_missing_directory(tmpdir):
     app = StaticFiles(directory=path)
     client = TestClient(app)
     with pytest.raises(RuntimeError) as exc:
-        response = client.get("/example.txt")
+        client.get("/example.txt")
     assert "does not exist" in str(exc)
 
 
@@ -125,7 +126,7 @@ def test_staticfiles_configured_with_file_instead_of_directory(tmpdir):
     app = StaticFiles(directory=path)
     client = TestClient(app)
     with pytest.raises(RuntimeError) as exc:
-        response = client.get("/example.txt")
+        client.get("/example.txt")
     assert "is not a directory" in str(exc)
 
 
@@ -133,9 +134,9 @@ def test_staticfiles_config_check_occurs_only_once(tmpdir):
     app = StaticFiles(directory=tmpdir)
     client = TestClient(app)
     assert not app.config_checked
-    response = client.get("/")
+    client.get("/")
     assert app.config_checked
-    response = client.get("/")
+    client.get("/")
     assert app.config_checked