diff --git a/crates/arr-db/migrations/0016_series_tvdb_id.sql b/crates/arr-db/migrations/0016_series_tvdb_id.sql
new file mode 100644
index 0000000..a893dc3
--- /dev/null
+++ b/crates/arr-db/migrations/0016_series_tvdb_id.sql
@@ -0,0 +1,6 @@
+-- Torznab `t=tvsearch` is addressed by TVDB id (§6.1); the title text query
+-- is only the fallback. Nullable, because TMDB does not know one for every
+-- series and #121 backfills it on refresh; unique when present so two rows
+-- cannot claim the same show.
+ALTER TABLE series ADD COLUMN tvdb_id INTEGER;
+CREATE UNIQUE INDEX series_tvdb_id_unique ON series (tvdb_id) WHERE tvdb_id IS NOT NULL;