diff --git a/clientapi/routing/leaveroom.go b/clientapi/routing/leaveroom.go
index 6d215c826..7e8c066eb 100644
--- a/clientapi/routing/leaveroom.go
+++ b/clientapi/routing/leaveroom.go
@@ -36,18 +36,11 @@ func LeaveRoomByID(
 			JSON: spec.Unknown("device userID is invalid"),
 		}
 	}
-	senderID, err := rsAPI.QuerySenderIDForUser(req.Context(), roomID, *userID)
-	if err != nil {
-		return util.JSONResponse{
-			Code: http.StatusBadRequest,
-			JSON: spec.Unknown("could not find senderID for this user"),
-		}
-	}
 
 	// Prepare to ask the roomserver to perform the room join.
 	leaveReq := roomserverAPI.PerformLeaveRequest{
 		RoomID: roomID,
-		Leaver: roomserverAPI.SenderUserIDPair{SenderID: senderID, UserID: *userID},
+		Leaver: *userID,
 	}
 	leaveRes := roomserverAPI.PerformLeaveResponse{}
 
diff --git a/roomserver/api/perform.go b/roomserver/api/perform.go
index af775e350..533fa52f6 100644
--- a/roomserver/api/perform.go
+++ b/roomserver/api/perform.go
@@ -47,7 +47,7 @@ type PerformJoinRequest struct {
 
 type PerformLeaveRequest struct {
 	RoomID string
-	Leaver SenderUserIDPair
+	Leaver spec.UserID
 }
 
 type PerformLeaveResponse struct {
diff --git a/roomserver/internal/perform/perform_admin.go b/roomserver/internal/perform/perform_admin.go
index a9ce63043..ec13bff87 100644
--- a/roomserver/internal/perform/perform_admin.go
+++ b/roomserver/internal/perform/perform_admin.go
@@ -170,13 +170,9 @@ func (r *Admin) PerformAdminEvacuateUser(
 	allRooms := append(roomIDs, inviteRoomIDs...)
 	affected = make([]string, 0, len(allRooms))
 	for _, roomID := range allRooms {
-		senderID, err := r.Queryer.QuerySenderIDForUser(ctx, roomID, *fullUserID)
-		if err != nil {
-			return nil, err
-		}
 		leaveReq := &api.PerformLeaveRequest{
 			RoomID: roomID,
-			Leaver: api.SenderUserIDPair{SenderID: senderID, UserID: *fullUserID},
+			Leaver: *fullUserID,
 		}
 		leaveRes := &api.PerformLeaveResponse{}
 		outputEvents, err := r.Leaver.PerformLeave(ctx, leaveReq, leaveRes)
diff --git a/roomserver/internal/perform/perform_leave.go b/roomserver/internal/perform/perform_leave.go
index 8fa324865..6687621f2 100644
--- a/roomserver/internal/perform/perform_leave.go
+++ b/roomserver/internal/perform/perform_leave.go
@@ -53,12 +53,12 @@ func (r *Leaver) PerformLeave(
 	req *api.PerformLeaveRequest,
 	res *api.PerformLeaveResponse,
 ) ([]api.OutputEvent, error) {
-	if !r.Cfg.Matrix.IsLocalServerName(req.Leaver.UserID.Domain()) {
-		return nil, fmt.Errorf("user %q does not belong to this homeserver", req.Leaver.UserID.String())
+	if !r.Cfg.Matrix.IsLocalServerName(req.Leaver.Domain()) {
+		return nil, fmt.Errorf("user %q does not belong to this homeserver", req.Leaver.String())
 	}
 	logger := logrus.WithContext(ctx).WithFields(logrus.Fields{
 		"room_id": req.RoomID,
-		"user_id": req.Leaver.UserID.String(),
+		"user_id": req.Leaver.String(),
 	})
 	logger.Info("User requested to leave join")
 	if strings.HasPrefix(req.RoomID, "!") {
@@ -78,9 +78,14 @@ func (r *Leaver) performLeaveRoomByID(
 	req *api.PerformLeaveRequest,
 	res *api.PerformLeaveResponse, // nolint:unparam
 ) ([]api.OutputEvent, error) {
+	leaver, err := r.RSAPI.QuerySenderIDForUser(ctx, req.RoomID, req.Leaver)
+	if err != nil {
+		return nil, fmt.Errorf("leaver %s has no matching senderID in this room", req.Leaver.String())
+	}
+
 	// If there's an invite outstanding for the room then respond to
 	// that.
-	isInvitePending, senderUser, eventID, _, err := helpers.IsInvitePending(ctx, r.DB, req.RoomID, req.Leaver.SenderID)
+	isInvitePending, senderUser, eventID, _, err := helpers.IsInvitePending(ctx, r.DB, req.RoomID, leaver)
 	if err == nil && isInvitePending {
 		sender, serr := r.RSAPI.QueryUserIDForSender(ctx, req.RoomID, senderUser)
 		if serr != nil || sender == nil {
@@ -88,12 +93,12 @@ func (r *Leaver) performLeaveRoomByID(
 		}
 		inviteSender := api.SenderUserIDPair{SenderID: senderUser, UserID: *sender}
 		if !r.Cfg.Matrix.IsLocalServerName(sender.Domain()) {
-			return r.performFederatedRejectInvite(ctx, req, res, inviteSender.UserID, eventID)
+			return r.performFederatedRejectInvite(ctx, req, res, inviteSender.UserID, eventID, leaver)
 		}
 		// check that this is not a "server notice room"
 		accData := &userapi.QueryAccountDataResponse{}
 		if err = r.UserAPI.QueryAccountData(ctx, &userapi.QueryAccountDataRequest{
-			UserID:   req.Leaver.UserID.String(),
+			UserID:   req.Leaver.String(),
 			RoomID:   req.RoomID,
 			DataType: "m.tag",
 		}, accData); err != nil {
@@ -124,7 +129,7 @@ func (r *Leaver) performLeaveRoomByID(
 		StateToFetch: []gomatrixserverlib.StateKeyTuple{
 			{
 				EventType: spec.MRoomMember,
-				StateKey:  string(req.Leaver.SenderID),
+				StateKey:  string(leaver),
 			},
 		},
 	}
@@ -138,18 +143,18 @@ func (r *Leaver) performLeaveRoomByID(
 
 	// Now let's see if the user is in the room.
 	if len(latestRes.StateEvents) == 0 {
-		return nil, fmt.Errorf("user %q is not a member of room %q", req.Leaver.UserID.String(), req.RoomID)
+		return nil, fmt.Errorf("user %q is not a member of room %q", req.Leaver.String(), req.RoomID)
 	}
 	membership, err := latestRes.StateEvents[0].Membership()
 	if err != nil {
 		return nil, fmt.Errorf("error getting membership: %w", err)
 	}
 	if membership != spec.Join && membership != spec.Invite {
-		return nil, fmt.Errorf("user %q is not joined to the room (membership is %q)", req.Leaver.UserID.String(), membership)
+		return nil, fmt.Errorf("user %q is not joined to the room (membership is %q)", req.Leaver.String(), membership)
 	}
 
 	// Prepare the template for the leave event.
-	senderIDString := string(req.Leaver.SenderID)
+	senderIDString := string(leaver)
 	proto := gomatrixserverlib.ProtoEvent{
 		Type:     spec.MRoomMember,
 		SenderID: senderIDString,
@@ -170,7 +175,7 @@ func (r *Leaver) performLeaveRoomByID(
 	// but everyone has since left. I suspect it does the wrong thing.
 
 	var buildRes rsAPI.QueryLatestEventsAndStateResponse
-	identity, err := r.Cfg.Matrix.SigningIdentityFor(req.Leaver.UserID.Domain())
+	identity, err := r.Cfg.Matrix.SigningIdentityFor(req.Leaver.Domain())
 	if err != nil {
 		return nil, fmt.Errorf("SigningIdentityFor: %w", err)
 	}
@@ -187,8 +192,8 @@ func (r *Leaver) performLeaveRoomByID(
 			{
 				Kind:         api.KindNew,
 				Event:        event,
-				Origin:       req.Leaver.UserID.Domain(),
-				SendAsServer: string(req.Leaver.UserID.Domain()),
+				Origin:       req.Leaver.Domain(),
+				SendAsServer: string(req.Leaver.Domain()),
 			},
 		},
 	}
@@ -206,11 +211,12 @@ func (r *Leaver) performFederatedRejectInvite(
 	req *api.PerformLeaveRequest,
 	res *api.PerformLeaveResponse, // nolint:unparam
 	inviteSender spec.UserID, eventID string,
+	leaver spec.SenderID,
 ) ([]api.OutputEvent, error) {
 	// Ask the federation sender to perform a federated leave for us.
 	leaveReq := fsAPI.PerformLeaveRequest{
 		RoomID:      req.RoomID,
-		UserID:      req.Leaver.UserID.String(),
+		UserID:      req.Leaver.String(),
 		ServerNames: []spec.ServerName{inviteSender.Domain()},
 	}
 	leaveRes := fsAPI.PerformLeaveResponse{}
@@ -225,7 +231,7 @@ func (r *Leaver) performFederatedRejectInvite(
 		util.GetLogger(ctx).WithError(err).Errorf("failed to get RoomInfo, still retiring invite event")
 	}
 
-	updater, err := r.DB.MembershipUpdater(ctx, req.RoomID, string(req.Leaver.SenderID), true, info.RoomVersion)
+	updater, err := r.DB.MembershipUpdater(ctx, req.RoomID, string(leaver), true, info.RoomVersion)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Errorf("failed to get MembershipUpdater, still retiring invite event")
 	}
@@ -251,7 +257,7 @@ func (r *Leaver) performFederatedRejectInvite(
 				EventID:        eventID,
 				RoomID:         req.RoomID,
 				Membership:     "leave",
-				TargetSenderID: req.Leaver.SenderID,
+				TargetSenderID: leaver,
 			},
 		},
 	}, nil