diff --git a/changelog.d/13766.bugfix b/changelog.d/13766.bugfix
new file mode 100644
index 000000000000..032c011315db
--- /dev/null
+++ b/changelog.d/13766.bugfix
@@ -0,0 +1 @@
+Make sequence cache_invalidation_stream_seq begins at 2.
diff --git a/synapse/storage/schema/main/delta/58/05cache_instance.sql.postgres b/synapse/storage/schema/main/delta/58/05cache_instance.sql.postgres
index aa46eb0e1033..f72a6f9459d9 100644
--- a/synapse/storage/schema/main/delta/58/05cache_instance.sql.postgres
+++ b/synapse/storage/schema/main/delta/58/05cache_instance.sql.postgres
@@ -27,4 +27,7 @@ CREATE TABLE cache_invalidation_stream_by_instance (
 
 CREATE UNIQUE INDEX cache_invalidation_stream_by_instance_id ON cache_invalidation_stream_by_instance(stream_id);
 
-CREATE SEQUENCE cache_invalidation_stream_seq;
+# The sequence needs to begin at 2 because a bunch of code assume that
+# get_next_id_txn will return values >= 2, cf this comment:
+# https://github.com/matrix-org/synapse/blob/b93bd95e8ab64d27ae26841020f62ee61272a5f2/synapse/storage/util/id_generators.py#L344
+CREATE SEQUENCE cache_invalidation_stream_seq MINVALUE 2;