diff --git a/state/migrations/20231108122539_clear_stuck_invites.go b/state/migrations/20231108122539_clear_stuck_invites.go
new file mode 100644
index 00000000..acd4afc8
--- /dev/null
+++ b/state/migrations/20231108122539_clear_stuck_invites.go
@@ -0,0 +1,83 @@
+package migrations
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"github.com/lib/pq"
+	"github.com/pressly/goose/v3"
+)
+
+func init() {
+	goose.AddMigrationContext(upClearStuckInvites, downClearStuckInvites)
+}
+
+// The purpose of this migration is to find users who have rooms which have
+// not been properly processed by the proxy and invalidate their since token
+// so they will do an initial sync on the next poller startup. This is specifically
+// targeting stuck invites, where there is an invite in the invites table but
+// the room is already joined. This is usually (always?) due to missing a create
+// event when the room was joined, caused by a synapse bug outlined in
+// https://github.com/matrix-org/sliding-sync/issues/367
+// This isn't exclusively a problem with invites, though it manifests more clearly there.
+func upClearStuckInvites(ctx context.Context, tx *sql.Tx) error {
+	// The syncv3_unread table is updated any time A) a room is in rooms.join and B) the unread count has changed,
+	// where nil != 0. Therefore, we can use this table as a proxy for "have we seen a v2 response which has put this
+	// room into rooms.join"? For every room in rooms.join, we should have seen a create event for it, and hence have
+	// an entry in syncv3_rooms. If we do not have an entry in syncv3_rooms but do have an entry in syncv3_unread, this
+	// implies we failed to properly store this joined room and therefore the user who the unread marker is for should be
+	// reset to force an initial sync. On matrix.org, of the users using sliding sync, this will catch around ~1.82% of users
+	rows, err := tx.QueryContext(ctx, `
+		SELECT distinct(user_id) FROM syncv3_unread
+		WHERE room_id NOT IN (
+			SELECT room_id
+			FROM syncv3_rooms
+		)
+	`)
+	defer rows.Close()
+	if err != nil {
+		return fmt.Errorf("failed to select bad users: %w", err)
+	}
+
+	var usersToInvalidate []string
+	for rows.Next() {
+		var userID string
+		err = rows.Scan(&userID)
+		if err != nil {
+			return fmt.Errorf("failed to scan user: %w", err)
+		}
+		usersToInvalidate = append(usersToInvalidate, userID)
+	}
+	logger.Info().Int("len_invalidate_users", len(usersToInvalidate)).Msg("invalidating users")
+	if len(usersToInvalidate) < 50 {
+		logger.Info().Strs("invalidate_users", usersToInvalidate).Msg("invalidating users")
+	}
+
+	// for each user:
+	// - reset their since token for all devices
+	// - remove any outstanding invites (we'll be told about them again when they initial sync)
+	res, err := tx.ExecContext(ctx, `
+	UPDATE syncv3_sync2_devices SET since='' WHERE user_id=ANY($1)
+	`, pq.StringArray(usersToInvalidate))
+	if err != nil {
+		return fmt.Errorf("failed to invalidate since tokens: %w", err)
+	}
+	ra, _ := res.RowsAffected()
+	logger.Info().Int64("num_devices", ra).Msg("reset since tokens")
+
+	res, err = tx.ExecContext(ctx, `
+	DELETE FROM syncv3_invites WHERE user_id=ANY($1)
+	`, pq.StringArray(usersToInvalidate))
+	if err != nil {
+		return fmt.Errorf("failed to remove outstanding invites: %w", err)
+	}
+	ra, _ = res.RowsAffected()
+	logger.Info().Int64("num_invites", ra).Msg("reset invites")
+	return nil
+}
+
+func downClearStuckInvites(ctx context.Context, tx *sql.Tx) error {
+	// we can't roll this back
+	return nil
+}
diff --git a/state/migrations/20231108122539_clear_stuck_invites_test.go b/state/migrations/20231108122539_clear_stuck_invites_test.go
new file mode 100644
index 00000000..616fd62e
--- /dev/null
+++ b/state/migrations/20231108122539_clear_stuck_invites_test.go
@@ -0,0 +1,232 @@
+package migrations
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/jmoiron/sqlx"
+	"github.com/matrix-org/sliding-sync/sqlutil"
+	"github.com/matrix-org/sliding-sync/state"
+	"github.com/matrix-org/sliding-sync/sync2"
+)
+
+func TestClearStuckInvites(t *testing.T) {
+	db, close := connectToDB(t)
+	defer close()
+	roomsTable := state.NewRoomsTable(db)
+	inviteTable := state.NewInvitesTable(db)
+	unreadTable := state.NewUnreadTable(db)
+	deviceTable := sync2.NewDevicesTable(db)
+	tokensTable := sync2.NewTokensTable(db, "secret")
+
+	zero := 0
+	device1 := "TEST_1"
+	device2 := "TEST_2"
+	roomA := "!TestClearStuckInvites_a:localhost"
+	roomB := "!TestClearStuckInvites_b:localhost"
+	roomC := "!TestClearStuckInvites_c:localhost"
+	roomD := "!TestClearStuckInvites_d:localhost"
+	roomE := "!TestClearStuckInvites_e:localhost"
+	roomF := "!TestClearStuckInvites_f:localhost"
+	roomG := "!TestClearStuckInvites_g:localhost"
+	alice := "@TestClearStuckInvites_alice:localhost"
+	bob := "@TestClearStuckInvites_bob:localhost"
+	charlie := "@TestClearStuckInvites_charlie:localhost"
+	doris := "@TestClearStuckInvites_doris:localhost"
+	users := []string{
+		alice, bob, charlie, doris,
+	}
+
+	// Test cases:
+	// Room | In Invite Table? | In Unread Table? | In Room Table? | Comment
+	//   A           Y                 Y                Y             OK, Genuine invite, proxy in room
+	//   B           Y                 Y                N             BAD, Stuck invite, proxy never saw join
+	//   C           Y                 N                Y             OK, Genuine invite, proxy in room, no unread counts (unusual but valid)
+	//   D           Y                 N                N             OK, Genuine invite, proxy not in room
+	//   E           N                 Y                Y             OK, Genuine joined room
+	//   F           N                 Y                N             BAD, Stuck joined room, proxy never saw join
+	//   G           N                 N                Y             OK, Genuine joined room, no unread counts (unusual but valid)
+	//   -           N                 N                N             Impossible, room id isn't in any table!
+	roomToInfo := map[string]struct {
+		invitedUser string
+		unreadUser  string
+		inRoomTable bool
+	}{
+		roomA: {
+			invitedUser: alice,
+			unreadUser:  bob,
+			inRoomTable: true,
+		},
+		roomB: {
+			invitedUser: bob,
+			unreadUser:  bob,
+			inRoomTable: false,
+		},
+		roomC: {
+			invitedUser: charlie,
+			inRoomTable: true,
+		},
+		roomD: {
+			invitedUser: doris,
+			inRoomTable: false,
+		},
+		roomE: {
+			unreadUser:  alice,
+			inRoomTable: true,
+		},
+		roomF: {
+			unreadUser: doris,
+		},
+		roomG: {
+			inRoomTable: true,
+		},
+	}
+
+	err := sqlutil.WithTransaction(db, func(txn *sqlx.Tx) error {
+		for roomID, info := range roomToInfo {
+			if info.inRoomTable {
+				err := roomsTable.Upsert(txn, state.RoomInfo{
+					ID: roomID,
+				}, 0, 0)
+				if err != nil {
+					return fmt.Errorf("Upsert room: %s", err)
+				}
+			}
+			if info.invitedUser != "" {
+				err := inviteTable.InsertInvite(info.invitedUser, roomID, []json.RawMessage{json.RawMessage(`{}`)})
+				if err != nil {
+					return fmt.Errorf("InsertInvite: %s", err)
+				}
+			}
+			if info.unreadUser != "" {
+				err := unreadTable.UpdateUnreadCounters(info.unreadUser, roomID, &zero, &zero)
+				if err != nil {
+					return fmt.Errorf("UpdateUnreadCounters: %s", err)
+				}
+			}
+		}
+		for _, userID := range users {
+			for _, deviceID := range []string{device1, device2} {
+				// each user has 2 devices
+				if err := deviceTable.InsertDevice(txn, userID, deviceID); err != nil {
+					return fmt.Errorf("InsertDevice: %s", err)
+				}
+				_, err := tokensTable.Insert(txn, userID+deviceID, userID, deviceID, time.Now())
+				if err != nil {
+					return fmt.Errorf("TokensTable.Insert: %s", err)
+				}
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("failed to set up test configuration: %s", err)
+	}
+	// set since tokens (this is done without a txn hence cannot be bundled in as the UPDATE would fail)
+	for _, userID := range users {
+		for i, deviceID := range []string{device1, device2} {
+			// each user has 2 devices
+			since := fmt.Sprintf("since_%d", i)
+			if err := deviceTable.UpdateDeviceSince(userID, deviceID, since); err != nil {
+				t.Fatalf("UpdateDeviceSince: %s", err)
+			}
+		}
+	}
+
+	t.Log("Run the migration.")
+	tx, err := db.Beginx()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := upClearStuckInvites(context.Background(), tx.Tx); err != nil {
+		t.Fatalf("upClearStuckInvites: %s", err)
+	}
+	tx.Commit()
+
+	// make a new txn for assertions
+	tx, err = db.Beginx()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// users in room B (bob) and F (doris) should be reset.
+	tokens, err := tokensTable.TokenForEachDevice(tx)
+	if err != nil {
+		t.Fatalf("TokenForEachDevice: %s", err)
+	}
+	wantResults := map[[2]string]struct {
+		wantSinceReset bool
+	}{
+		{bob, device1}: {
+			wantSinceReset: true,
+		},
+		{bob, device2}: {
+			wantSinceReset: true,
+		},
+		{doris, device1}: {
+			wantSinceReset: true,
+		},
+		{doris, device2}: {
+			wantSinceReset: true,
+		},
+		// everyone else should NOT have since reset
+		{alice, device1}: {
+			wantSinceReset: false,
+		},
+		{alice, device2}: {
+			wantSinceReset: false,
+		},
+		{charlie, device1}: {
+			wantSinceReset: false,
+		},
+		{charlie, device2}: {
+			wantSinceReset: false,
+		},
+	}
+	for _, tok := range tokens {
+		key := [2]string{tok.UserID, tok.DeviceID}
+		want, ok := wantResults[key]
+		if !ok {
+			continue // different user in another test?
+		}
+		if want.wantSinceReset && tok.Since != "" {
+			t.Errorf("%s want since reset, got %+v", key, tok)
+		}
+		if !want.wantSinceReset && tok.Since == "" {
+			t.Errorf("%s did not want since reset, got %+v", key, tok)
+		}
+	}
+	// invites for Bob and Doris are gone
+	for _, userID := range []string{bob, doris} {
+		got, err := inviteTable.SelectAllInvitesForUser(userID)
+		if err != nil {
+			t.Fatalf("SelectAllInvitesForUser: %s", err)
+		}
+		if len(got) > 0 {
+			t.Fatalf("SelectAllInvitesForUser got invites for %s, wanted none: %+v", userID, got)
+		}
+	}
+	// ensure other invites remain
+	wantInvites := map[string][]string{
+		alice:   {roomA},
+		charlie: {roomC},
+	}
+	for userID, wantInvitesRooms := range wantInvites {
+		got, err := inviteTable.SelectAllInvitesForUser(userID)
+		if err != nil {
+			t.Fatalf("SelectAllInvitesForUser: %s", err)
+		}
+		if len(got) != len(wantInvitesRooms) {
+			t.Fatalf("SelectAllInvitesForUser got %d invites for %s, wanted %d", len(got), userID, len(wantInvitesRooms))
+		}
+		for _, wantRoom := range wantInvitesRooms {
+			_, exists := got[wantRoom]
+			if !exists {
+				t.Fatalf("SelectAllInvitesForUser wanted invite for %s in %s, but it's missing", userID, wantRoom)
+			}
+		}
+	}
+}