diff --git a/mail4one/pop3.py b/mail4one/pop3.py
index 9600de8..f6bde47 100644
--- a/mail4one/pop3.py
+++ b/mail4one/pop3.py
@@ -219,8 +219,8 @@ def trans_command_retr(mails: MailList, req: Request) -> None:
         write(ok("Contents follow"))
         with get_mail_fp(entry) as fp:
             for line in fp:
-                if line.startswith(b'.'):
-                    write(b'.') # prepend dot
+                if line.startswith(b"."):
+                    write(b".")  # prepend dot
                 write(line)
         # write(get_mail(entry)) # no prepend dot
         write(end())
@@ -396,9 +396,9 @@ def debug_main():
     _, mails_path, mbox = sys.argv
 
     mails_path = Path(mails_path)
-    users = [ User(username="dummy", password_hash=gen_pwhash("dummy"), mbox=mbox) ]
+    users = [User(username="dummy", password_hash=gen_pwhash("dummy"), mbox=mbox)]
 
-    asyncio.run(a_main("127.0.0.1", 1101,  mails_path, users=users))
+    asyncio.run(a_main("127.0.0.1", 1101, mails_path, users=users))
 
 
 if __name__ == "__main__":
diff --git a/tests/test_pop.py b/tests/test_pop.py
index f5def85..1e17d38 100644
--- a/tests/test_pop.py
+++ b/tests/test_pop.py
@@ -218,14 +218,15 @@ class TestPop3(unittest.IsolatedAsyncioTestCase):
             pc = poplib.POP3("127.0.0.1", 7995)
             try:
                 self.assertEqual(b"+OK Server Ready", pc.getwelcome())
-                self.assertEqual(b'+OK Welcome', pc.user("foo2"))
-                self.assertEqual(b'+OK Login successful', pc.pass_("helloworld"))
+                self.assertEqual(b"+OK Welcome", pc.user("foo2"))
+                self.assertEqual(b"+OK Login successful", pc.pass_("helloworld"))
                 _, eml, oc = pc.retr(1)
                 self.assertIn(b"Previous line just has a dot", eml)
                 self.assertIn(b".Line starts with a dot", eml)
                 self.assertIn(b".", eml)
             finally:
                 pc.quit()
+
         await asyncio.to_thread(run_poplib)
 
     async def asyncTearDown(self) -> None: