diff --git a/synapse/crypto/context_factory.py b/synapse/crypto/context_factory.py
index bfd7910f30..3faca79200 100644
--- a/synapse/crypto/context_factory.py
+++ b/synapse/crypto/context_factory.py
@@ -21,12 +21,8 @@ from OpenSSL import SSL, crypto
 from twisted.internet._sslverify import _defaultCurveName
 from twisted.internet.abstract import isIPAddress, isIPv6Address
 from twisted.internet.interfaces import IOpenSSLClientConnectionCreator
-from twisted.internet.ssl import (
-    CertificateOptions,
-    ContextFactory,
-    OpenSSLCertificateAuthorities,
-    platformTrust,
-)
+from twisted.internet.ssl import CertificateOptions, ContextFactory, platformTrust
+from twisted.internet._sslverify import OpenSSLCertificateAuthorities
 from twisted.python.failure import Failure
 
 logger = logging.getLogger(__name__)