diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index eca8513905..eecf3b0b2a 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -13,22 +13,22 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
+
+import pymacaroons
 from canonicaljson import encode_canonical_json
 from signedjson.key import decode_verify_key_bytes
 from signedjson.sign import verify_signed_json, SignatureVerifyException
-
 from twisted.internet import defer
-
-from synapse.api.constants import EventTypes, Membership, JoinRules
-from synapse.api.errors import AuthError, Codes, SynapseError, EventSizeError
-from synapse.types import Requester, UserID, get_domain_from_id
-from synapse.util.logutils import log_function
-from synapse.util.logcontext import preserve_context_over_fn
-from synapse.util.metrics import Measure
 from unpaddedbase64 import decode_base64
 
-import logging
-import pymacaroons
+import synapse.types
+from synapse.api.constants import EventTypes, Membership, JoinRules
+from synapse.api.errors import AuthError, Codes, SynapseError, EventSizeError
+from synapse.types import UserID, get_domain_from_id
+from synapse.util.logcontext import preserve_context_over_fn
+from synapse.util.logutils import log_function
+from synapse.util.metrics import Measure
 
 logger = logging.getLogger(__name__)
 
@@ -566,8 +566,7 @@ class Auth(object):
         Args:
             request - An HTTP request with an access_token query parameter.
         Returns:
-            defer.Deferred: resolves to a namedtuple including "user" (UserID)
-            "access_token_id" (int), "is_guest" (bool)
+            defer.Deferred: resolves to a ``synapse.types.Requester`` object
         Raises:
             AuthError if no user by that token exists or the token is invalid.
         """
@@ -576,9 +575,7 @@ class Auth(object):
             user_id = yield self._get_appservice_user_id(request.args)
             if user_id:
                 request.authenticated_entity = user_id
-                defer.returnValue(
-                    Requester(UserID.from_string(user_id), "", False)
-                )
+                defer.returnValue(synapse.types.create_requester(user_id))
 
             access_token = request.args["access_token"][0]
             user_info = yield self.get_user_by_access_token(access_token, rights)
@@ -612,7 +609,8 @@ class Auth(object):
 
             request.authenticated_entity = user.to_string()
 
-            defer.returnValue(Requester(user, token_id, is_guest))
+            defer.returnValue(synapse.types.create_requester(
+                user, token_id, is_guest, device_id))
         except KeyError:
             raise AuthError(
                 self.TOKEN_NOT_FOUND_HTTP_STATUS, "Missing access token.",
diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
index 6264aa0d9a..11081a0cd5 100644
--- a/synapse/handlers/_base.py
+++ b/synapse/handlers/_base.py
@@ -13,14 +13,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
+
 from twisted.internet import defer
 
-from synapse.api.errors import LimitExceededError
+import synapse.types
 from synapse.api.constants import Membership, EventTypes
-from synapse.types import UserID, Requester
-
-
-import logging
+from synapse.api.errors import LimitExceededError
+from synapse.types import UserID
 
 
 logger = logging.getLogger(__name__)
@@ -124,7 +124,8 @@ class BaseHandler(object):
                 # and having homeservers have their own users leave keeps more
                 # of that decision-making and control local to the guest-having
                 # homeserver.
-                requester = Requester(target_user, "", True)
+                requester = synapse.types.create_requester(
+                    target_user, is_guest=True)
                 handler = self.hs.get_handlers().room_member_handler
                 yield handler.update_membership(
                     requester,
diff --git a/synapse/handlers/profile.py b/synapse/handlers/profile.py
index 711a6a567f..d9ac09078d 100644
--- a/synapse/handlers/profile.py
+++ b/synapse/handlers/profile.py
@@ -13,15 +13,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
+
 from twisted.internet import defer
 
+import synapse.types
 from synapse.api.errors import SynapseError, AuthError, CodeMessageException
-from synapse.types import UserID, Requester
-
+from synapse.types import UserID
 from ._base import BaseHandler
 
-import logging
-
 
 logger = logging.getLogger(__name__)
 
@@ -165,7 +165,9 @@ class ProfileHandler(BaseHandler):
             try:
                 # Assume the user isn't a guest because we don't let guests set
                 # profile or avatar data.
-                requester = Requester(user, "", False)
+                # XXX why are we recreating `requester` here for each room?
+                # what was wrong with the `requester` we were passed?
+                requester = synapse.types.create_requester(user)
                 yield handler.update_membership(
                     requester,
                     user,
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 94b19d0cb0..b9b5880d64 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -14,18 +14,19 @@
 # limitations under the License.
 
 """Contains functions for registering clients."""
+import logging
+import urllib
+
 from twisted.internet import defer
 
-from synapse.types import UserID, Requester
+import synapse.types
 from synapse.api.errors import (
     AuthError, Codes, SynapseError, RegistrationError, InvalidCaptchaError
 )
-from ._base import BaseHandler
-from synapse.util.async import run_on_reactor
 from synapse.http.client import CaptchaServerHttpClient
-
-import logging
-import urllib
+from synapse.types import UserID
+from synapse.util.async import run_on_reactor
+from ._base import BaseHandler
 
 logger = logging.getLogger(__name__)
 
@@ -410,8 +411,9 @@ class RegistrationHandler(BaseHandler):
         if displayname is not None:
             logger.info("setting user display name: %s -> %s", user_id, displayname)
             profile_handler = self.hs.get_handlers().profile_handler
+            requester = synapse.types.create_requester(user)
             yield profile_handler.set_displayname(
-                user, Requester(user, token, False), displayname
+                user, requester, displayname
             )
 
         defer.returnValue((user_id, token))
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 7e616f44fd..8cec8fc4ed 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -14,24 +14,22 @@
 # limitations under the License.
 
 
+import logging
+
+from signedjson.key import decode_verify_key_bytes
+from signedjson.sign import verify_signed_json
 from twisted.internet import defer
+from unpaddedbase64 import decode_base64
 
-from ._base import BaseHandler
-
-from synapse.types import UserID, RoomID, Requester
+import synapse.types
 from synapse.api.constants import (
     EventTypes, Membership,
 )
 from synapse.api.errors import AuthError, SynapseError, Codes
+from synapse.types import UserID, RoomID
 from synapse.util.async import Linearizer
 from synapse.util.distributor import user_left_room, user_joined_room
-
-from signedjson.sign import verify_signed_json
-from signedjson.key import decode_verify_key_bytes
-
-from unpaddedbase64 import decode_base64
-
-import logging
+from ._base import BaseHandler
 
 logger = logging.getLogger(__name__)
 
@@ -315,7 +313,7 @@ class RoomMemberHandler(BaseHandler):
             )
             assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
         else:
-            requester = Requester(target_user, None, False)
+            requester = synapse.types.create_requester(target_user)
 
         message_handler = self.hs.get_handlers().message_handler
         prev_event = message_handler.deduplicate_state_event(event, context)
diff --git a/synapse/rest/client/v2_alpha/keys.py b/synapse/rest/client/v2_alpha/keys.py
index 89ab39491c..56364af337 100644
--- a/synapse/rest/client/v2_alpha/keys.py
+++ b/synapse/rest/client/v2_alpha/keys.py
@@ -13,18 +13,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
+
+import simplejson as json
+from canonicaljson import encode_canonical_json
 from twisted.internet import defer
 
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
 from synapse.types import UserID
-
-from canonicaljson import encode_canonical_json
-
 from ._base import client_v2_patterns
 
-import logging
-import simplejson as json
-
 logger = logging.getLogger(__name__)
 
 
diff --git a/synapse/types.py b/synapse/types.py
index f639651a73..5349b0c450 100644
--- a/synapse/types.py
+++ b/synapse/types.py
@@ -18,7 +18,38 @@ from synapse.api.errors import SynapseError
 from collections import namedtuple
 
 
-Requester = namedtuple("Requester", ["user", "access_token_id", "is_guest"])
+Requester = namedtuple("Requester",
+                       ["user", "access_token_id", "is_guest", "device_id"])
+"""
+Represents the user making a request
+
+Attributes:
+    user (UserID):  id of the user making the request
+    access_token_id (int|None):  *ID* of the access token used for this
+        request, or None if it came via the appservice API or similar
+    is_guest (bool):  True if the user making this request is a guest user
+    device_id (str|None):  device_id which was set at authentication time
+"""
+
+
+def create_requester(user_id, access_token_id=None, is_guest=False,
+                     device_id=None):
+    """
+    Create a new ``Requester`` object
+
+    Args:
+        user_id (str|UserID):  id of the user making the request
+        access_token_id (int|None):  *ID* of the access token used for this
+            request, or None if it came via the appservice API or similar
+        is_guest (bool):  True if the user making this request is a guest user
+        device_id (str|None):  device_id which was set at authentication time
+
+    Returns:
+        Requester
+    """
+    if not isinstance(user_id, UserID):
+        user_id = UserID.from_string(user_id)
+    return Requester(user_id, access_token_id, is_guest, device_id)
 
 
 def get_domain_from_id(string):
diff --git a/tests/handlers/test_profile.py b/tests/handlers/test_profile.py
index 4f2c14e4ff..f1f664275f 100644
--- a/tests/handlers/test_profile.py
+++ b/tests/handlers/test_profile.py
@@ -19,11 +19,12 @@ from twisted.internet import defer
 
 from mock import Mock, NonCallableMock
 
+import synapse.types
 from synapse.api.errors import AuthError
 from synapse.handlers.profile import ProfileHandler
 from synapse.types import UserID
 
-from tests.utils import setup_test_homeserver, requester_for_user
+from tests.utils import setup_test_homeserver
 
 
 class ProfileHandlers(object):
@@ -86,7 +87,7 @@ class ProfileTestCase(unittest.TestCase):
     def test_set_my_name(self):
         yield self.handler.set_displayname(
             self.frank,
-            requester_for_user(self.frank),
+            synapse.types.create_requester(self.frank),
             "Frank Jr."
         )
 
@@ -99,7 +100,7 @@ class ProfileTestCase(unittest.TestCase):
     def test_set_my_name_noauth(self):
         d = self.handler.set_displayname(
             self.frank,
-            requester_for_user(self.bob),
+            synapse.types.create_requester(self.bob),
             "Frank Jr."
         )
 
@@ -144,7 +145,8 @@ class ProfileTestCase(unittest.TestCase):
     @defer.inlineCallbacks
     def test_set_my_avatar(self):
         yield self.handler.set_avatar_url(
-            self.frank, requester_for_user(self.frank), "http://my.server/pic.gif"
+            self.frank, synapse.types.create_requester(self.frank),
+            "http://my.server/pic.gif"
         )
 
         self.assertEquals(
diff --git a/tests/replication/test_resource.py b/tests/replication/test_resource.py
index 842e3d29d7..e70ac6f14d 100644
--- a/tests/replication/test_resource.py
+++ b/tests/replication/test_resource.py
@@ -13,15 +13,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.replication.resource import ReplicationResource
-from synapse.types import Requester, UserID
-
-from twisted.internet import defer
-from tests import unittest
-from tests.utils import setup_test_homeserver, requester_for_user
-from mock import Mock, NonCallableMock
-import json
 import contextlib
+import json
+
+from mock import Mock, NonCallableMock
+from twisted.internet import defer
+
+import synapse.types
+from synapse.replication.resource import ReplicationResource
+from synapse.types import UserID
+from tests import unittest
+from tests.utils import setup_test_homeserver
 
 
 class ReplicationResourceCase(unittest.TestCase):
@@ -61,7 +63,7 @@ class ReplicationResourceCase(unittest.TestCase):
     def test_events_and_state(self):
         get = self.get(events="-1", state="-1", timeout="0")
         yield self.hs.get_handlers().room_creation_handler.create_room(
-            Requester(self.user, "", False), {}
+            synapse.types.create_requester(self.user), {}
         )
         code, body = yield get
         self.assertEquals(code, 200)
@@ -144,7 +146,7 @@ class ReplicationResourceCase(unittest.TestCase):
     def send_text_message(self, room_id, message):
         handler = self.hs.get_handlers().message_handler
         event = yield handler.create_and_send_nonmember_event(
-            requester_for_user(self.user),
+            synapse.types.create_requester(self.user),
             {
                 "type": "m.room.message",
                 "content": {"body": "message", "msgtype": "m.text"},
@@ -157,7 +159,7 @@ class ReplicationResourceCase(unittest.TestCase):
     @defer.inlineCallbacks
     def create_room(self):
         result = yield self.hs.get_handlers().room_creation_handler.create_room(
-            Requester(self.user, "", False), {}
+            synapse.types.create_requester(self.user), {}
         )
         defer.returnValue(result["room_id"])
 
diff --git a/tests/rest/client/v1/test_profile.py b/tests/rest/client/v1/test_profile.py
index af02fce8fb..1e95e97538 100644
--- a/tests/rest/client/v1/test_profile.py
+++ b/tests/rest/client/v1/test_profile.py
@@ -14,17 +14,14 @@
 # limitations under the License.
 
 """Tests REST events for /profile paths."""
-from tests import unittest
+from mock import Mock
 from twisted.internet import defer
 
-from mock import Mock
-
-from ....utils import MockHttpResource, setup_test_homeserver
-
+import synapse.types
 from synapse.api.errors import SynapseError, AuthError
-from synapse.types import Requester, UserID
-
 from synapse.rest.client.v1 import profile
+from tests import unittest
+from ....utils import MockHttpResource, setup_test_homeserver
 
 myid = "@1234ABCD:test"
 PATH_PREFIX = "/_matrix/client/api/v1"
@@ -52,7 +49,7 @@ class ProfileTestCase(unittest.TestCase):
         )
 
         def _get_user_by_req(request=None, allow_guest=False):
-            return Requester(UserID.from_string(myid), "", False)
+            return synapse.types.create_requester(myid)
 
         hs.get_v1auth().get_user_by_req = _get_user_by_req
 
diff --git a/tests/utils.py b/tests/utils.py
index ed547bc39b..915b934e94 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -20,7 +20,6 @@ from synapse.storage.prepare_database import prepare_database
 from synapse.storage.engines import create_engine
 from synapse.server import HomeServer
 from synapse.federation.transport import server
-from synapse.types import Requester
 from synapse.util.ratelimitutils import FederationRateLimiter
 
 from synapse.util.logcontext import LoggingContext
@@ -512,7 +511,3 @@ class DeferredMockCallable(object):
                     "call(%s)" % _format_call(c[0], c[1]) for c in calls
                 ])
             )
-
-
-def requester_for_user(user):
-    return Requester(user, None, False)