diff --git a/changelog.d/5177.bugfix b/changelog.d/5177.bugfix
new file mode 100644
index 0000000000..c2f1644ae5
--- /dev/null
+++ b/changelog.d/5177.bugfix
@@ -0,0 +1 @@
+Fix 3pid guest invites.
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index ffc588d454..93ac986c86 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -944,7 +944,7 @@ class RoomMemberHandler(object):
         }
 
         if self.config.invite_3pid_guest:
-            guest_access_token, guest_user_id = yield self.get_or_register_3pid_guest(
+            guest_user_id, guest_access_token = yield self.get_or_register_3pid_guest(
                 requester=requester,
                 medium=medium,
                 address=address,