diff --git a/jetforce/protocol.py b/jetforce/protocol.py
index afdeea9..a8bfc3e 100644
--- a/jetforce/protocol.py
+++ b/jetforce/protocol.py
@@ -6,7 +6,7 @@ import typing
 import urllib.parse
 
 from twisted.internet.address import IPv4Address, IPv6Address
-from twisted.internet.defer import Deferred, ensureDeferred, CancelledError
+from twisted.internet.defer import CancelledError, Deferred, ensureDeferred
 from twisted.internet.protocol import connectionDone
 from twisted.internet.task import deferLater
 from twisted.protocols.basic import LineOnlyReceiver
diff --git a/setup.py b/setup.py
index 0ce0d51..6ea9476 100644
--- a/setup.py
+++ b/setup.py
@@ -17,7 +17,8 @@ setuptools.setup(
     author_email="lazar.michael22@gmail.com",
     description="An Experimental Gemini Server",
     install_requires=[
-        "twisted>=20.3.0",
+        # 21.2.0 introduces a bunch of broken type hints
+        "twisted>=20.3.0,<21.2.0",
         # Requirements below are used by twisted[security]
         "service_identity",
         "idna",