diff --git a/changelog.d/4088.bugfix b/changelog.d/4088.bugfix
new file mode 100644
index 0000000000..61722b6224
--- /dev/null
+++ b/changelog.d/4088.bugfix
@@ -0,0 +1 @@
+Added domain validation when including a list of invitees upon room creation.
\ No newline at end of file
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 970be3c846..2816bd8f87 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -28,6 +28,7 @@ from twisted.internet import defer
 from synapse.api.constants import EventTypes, JoinRules, RoomCreationPreset
 from synapse.api.errors import AuthError, Codes, NotFoundError, StoreError, SynapseError
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
+from synapse.http.endpoint import parse_and_validate_server_name
 from synapse.storage.state import StateFilter
 from synapse.types import RoomAlias, RoomID, RoomStreamToken, StreamToken, UserID
 from synapse.util import stringutils
@@ -554,7 +555,8 @@ class RoomCreationHandler(BaseHandler):
         invite_list = config.get("invite", [])
         for i in invite_list:
             try:
-                UserID.from_string(i)
+                uid = UserID.from_string(i)
+                parse_and_validate_server_name(uid.domain)
             except Exception:
                 raise SynapseError(400, "Invalid user_id: %s" % (i,))
 
diff --git a/tests/rest/client/v1/test_rooms.py b/tests/rest/client/v1/test_rooms.py
index fe741637f5..2f2ca74611 100644
--- a/tests/rest/client/v1/test_rooms.py
+++ b/tests/rest/client/v1/test_rooms.py
@@ -484,6 +484,15 @@ class RoomsCreateTestCase(RoomBase):
         self.render(request)
         self.assertEquals(400, channel.code)
 
+    def test_post_room_invitees_invalid_mxid(self):
+        # POST with invalid invitee, see https://github.com/matrix-org/synapse/issues/4088
+        # Note the trailing space in the MXID here!
+        request, channel = self.make_request(
+            "POST", "/createRoom", b'{"invite":["@alice:example.com "]}'
+        )
+        self.render(request)
+        self.assertEquals(400, channel.code)
+
 
 class RoomTopicTestCase(RoomBase):
     """ Tests /rooms/$room_id/topic REST events. """