diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index d3f4b9d543..76d2d2d640 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -34,6 +34,7 @@ class RegistrationConfig(Config):
         self.registration_shared_secret = config.get("registration_shared_secret")
         self.macaroon_secret_key = config.get("macaroon_secret_key")
         self.bcrypt_rounds = config.get("bcrypt_rounds", 12)
+        self.trusted_third_party_id_servers = config["trusted_third_party_id_servers"]
         self.allow_guest_access = config.get("allow_guest_access", False)
 
     def default_config(self, **kwargs):
@@ -60,6 +61,12 @@ class RegistrationConfig(Config):
         # participate in rooms hosted on this server which have been made
         # accessible to anonymous users.
         allow_guest_access: False
+
+        # The list of identity servers trusted to verify third party
+        # identifiers by this server.
+        trusted_third_party_id_servers:
+            - matrix.org
+            - vector.im
         """ % locals()
 
     def add_arguments(self, parser):
diff --git a/synapse/handlers/identity.py b/synapse/handlers/identity.py
index 819ec57c4f..656ce124f9 100644
--- a/synapse/handlers/identity.py
+++ b/synapse/handlers/identity.py
@@ -36,14 +36,15 @@ class IdentityHandler(BaseHandler):
 
         self.http_client = hs.get_simple_http_client()
 
+        self.trusted_id_servers = set(hs.config.trusted_third_party_id_servers)
+        self.trust_any_id_server_just_for_testing_do_not_use = (
+            hs.config.use_insecure_ssl_client_just_for_testing_do_not_use
+        )
+
     @defer.inlineCallbacks
     def threepid_from_creds(self, creds):
         yield run_on_reactor()
 
-        # XXX: make this configurable!
-        # trustedIdServers = ['matrix.org', 'localhost:8090']
-        trustedIdServers = ['matrix.org', 'vector.im']
-
         if 'id_server' in creds:
             id_server = creds['id_server']
         elif 'idServer' in creds:
@@ -58,10 +59,19 @@ class IdentityHandler(BaseHandler):
         else:
             raise SynapseError(400, "No client_secret in creds")
 
-        if id_server not in trustedIdServers:
-            logger.warn('%s is not a trusted ID server: rejecting 3pid ' +
-                        'credentials', id_server)
-            defer.returnValue(None)
+        if id_server not in self.trusted_id_servers:
+            if self.trust_any_id_server_just_for_testing_do_not_use:
+                logger.warn(
+                    "Trusting untrustworthy ID server %r even though it isn't"
+                    " in the trusted id list for testing because"
+                    " 'use_insecure_ssl_client_just_for_testing_do_not_use'"
+                    " is set in the config",
+                    id_server,
+                )
+            else:
+                logger.warn('%s is not a trusted ID server: rejecting 3pid ' +
+                            'credentials', id_server)
+                defer.returnValue(None)
 
         data = {}
         try:
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index d507172704..a614b79d45 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -116,9 +116,10 @@ class ThreepidRestServlet(RestServlet):
 
         body = parse_json_dict_from_request(request)
 
-        if 'threePidCreds' not in body:
+        threePidCreds = body.get('threePidCreds')
+        threePidCreds = body.get('three_pid_creds', threePidCreds)
+        if threePidCreds is None:
             raise SynapseError(400, "Missing param", Codes.MISSING_PARAM)
-        threePidCreds = body['threePidCreds']
 
         requester = yield self.auth.get_user_by_req(request)
         user_id = requester.user.to_string()
diff --git a/tests/utils.py b/tests/utils.py
index 43cc2b30cd..431252a6f1 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -49,6 +49,7 @@ def setup_test_homeserver(name="test", datastore=None, config=None, **kargs):
         config.disable_registration = False
         config.macaroon_secret_key = "not even a little secret"
         config.server_name = "server.under.test"
+        config.trusted_third_party_id_servers = []
 
     if "clock" not in kargs:
         kargs["clock"] = MockClock()