diff --git a/synapse/config/tls.py b/synapse/config/tls.py
index b09dc986ab..b66154bc7c 100644
--- a/synapse/config/tls.py
+++ b/synapse/config/tls.py
@@ -47,10 +47,6 @@ class TlsConfig(Config):
 
         self.tls_fingerprints = config["tls_fingerprints"]
 
-        self.tls_ignore_certificate_validation = config.get(
-            "tls_ignore_certificate_validation", False
-        )
-
         # Check that our own certificate is included in the list of fingerprints
         # and include it if it is not.
         x509_certificate_bytes = crypto.dump_certificate(
@@ -77,8 +73,6 @@ class TlsConfig(Config):
         tls_private_key_path = base_key_name + ".tls.key"
         tls_dh_params_path = base_key_name + ".tls.dh"
 
-        tls_ignore_certificate_validation = False
-
         return """\
         # PEM encoded X509 certificate for TLS.
         # You can replace the self-signed certificate that synapse
@@ -123,11 +117,6 @@ class TlsConfig(Config):
         #
         tls_fingerprints: []
         # tls_fingerprints: [{"sha256": "<base64_encoded_sha256_fingerprint>"}]
-
-        # Ignore certificate validation for TLS client connections to other
-        # homeservers using federation. Don't enable this in a production
-        # environment, unless you know what you are doing!
-        tls_ignore_certificate_validation: %(tls_ignore_certificate_validation)s
         """ % locals()
 
     def read_tls_certificate(self, cert_path):
diff --git a/synapse/crypto/context_factory.py b/synapse/crypto/context_factory.py
index 415899e62b..e93afbf975 100644
--- a/synapse/crypto/context_factory.py
+++ b/synapse/crypto/context_factory.py
@@ -11,18 +11,19 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
-from twisted.internet import ssl
-from OpenSSL import SSL, crypto
-from twisted.internet._sslverify import _defaultCurveName, ClientTLSOptions, \
-    OpenSSLCertificateOptions, optionsForClientTLS
-
 import logging
 
+import idna
+from OpenSSL import SSL, crypto
+from twisted.internet.ssl import ContextFactory, CertificateOptions
+from twisted.internet._sslverify import _defaultCurveName, _tolerateErrors
+from twisted.internet.interfaces import IOpenSSLClientConnectionCreator
+from zope.interface import implementer
+
 logger = logging.getLogger(__name__)
 
 
-class ServerContextFactory(ssl.ContextFactory):
+class ServerContextFactory(ContextFactory):
     """Factory for PyOpenSSL SSL contexts that are used to handle incoming
     connections and to make connections to remote servers."""
 
@@ -51,18 +52,31 @@ class ServerContextFactory(ssl.ContextFactory):
         return self._context
 
 
-class ClientTLSOptionsNoCertVerification(ClientTLSOptions):
-    """Redefinition of ClientTLSOptions to completely ignore certificate
-    validation. Should be kept in sync with the original class in Twisted.
-    This version of ClientTLSOptions is only intended for development use."""
+@implementer(IOpenSSLClientConnectionCreator)
+class ClientTLSOptions(object):
+    """
+    Client creator for TLS without certificate identity verification. This is a
+    copy of twisted.internet._sslverify.ClientTLSOptions with the identity
+    verification left out. For documentation, see the twisted documentation.
+    """
 
-    def __init__(self, *args, **kwargs):
-        super(ClientTLSOptionsNoCertVerification, self).__init__(*args, **kwargs)
+    def __init__(self, hostname, ctx):
+        self._ctx = ctx
+        self._hostname = hostname
+        self._hostnameBytes = idna.encode(hostname)
+        ctx.set_info_callback(
+            _tolerateErrors(self._identityVerifyingInfoCallback)
+        )
 
-        def do_nothing(*_args, **_kwargs):
-            pass
+    def clientConnectionForTLS(self, tlsProtocol):
+        context = self._ctx
+        connection = SSL.Connection(context, None)
+        connection.set_app_data(tlsProtocol)
+        return connection
 
-        self._ctx.set_info_callback(do_nothing)
+    def _identityVerifyingInfoCallback(self, connection, where, ret):
+        if where & SSL.SSL_CB_HANDSHAKE_START:
+            connection.set_tlsext_host_name(self._hostnameBytes)
 
 
 class ClientTLSOptionsFactory(object):
@@ -70,13 +84,11 @@ class ClientTLSOptionsFactory(object):
     to remote servers for federation."""
 
     def __init__(self, config):
-        self._ignore_certificate_validation = config.tls_ignore_certificate_validation
+        # We don't use config options yet
+        pass
 
     def get_options(self, host):
-        if self._ignore_certificate_validation:
-            return ClientTLSOptionsNoCertVerification(
-                unicode(host),
-                OpenSSLCertificateOptions(verify=False).getContext()
-            )
-        else:
-            return optionsForClientTLS(unicode(host))
+        return ClientTLSOptions(
+            unicode(host),
+            CertificateOptions(verify=False).getContext()
+        )
diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
index abf4862084..39432da452 100644
--- a/synapse/http/endpoint.py
+++ b/synapse/http/endpoint.py
@@ -65,7 +65,7 @@ def matrix_federation_endpoint(reactor, destination, tls_client_options_factory=
     else:
         def transport_endpoint(reactor, host, port, timeout):
             return wrapClientTLS(
-                tls_client_options_factory.get_options(unicode(host)),
+                tls_client_options_factory.get_options(host),
                 HostnameEndpoint(reactor, host, port, timeout=timeout))
         default_port = 8448