diff --git a/db/migrations/postgres/000099_fix_blockchainevent_protocolid_index.up.sql b/db/migrations/postgres/000099_fix_blockchainevent_protocolid_index.up.sql
index 9fbc171185..6acdb7dfc6 100644
--- a/db/migrations/postgres/000099_fix_blockchainevent_protocolid_index.up.sql
+++ b/db/migrations/postgres/000099_fix_blockchainevent_protocolid_index.up.sql
@@ -1,5 +1,7 @@
 BEGIN;
 DROP INDEX blockchainevents_protocolid;
+DELETE FROM blockchainevents WHERE listener_id IS NULL AND seq NOT IN (
+  SELECT MIN(seq) FROM blockchainevents WHERE listener_id IS NULL GROUP BY namespace, protocol_id);
 CREATE UNIQUE INDEX blockchainevents_protocolid ON blockchainevents(namespace, protocol_id) WHERE listener_id IS NULL;
 CREATE UNIQUE INDEX blockchainevents_listener_protocolid ON blockchainevents(namespace, listener_id, protocol_id) WHERE listener_id IS NOT NULL;
 COMMIT;
diff --git a/db/migrations/sqlite/000099_fix_blockchainevent_protocolid_index.up.sql b/db/migrations/sqlite/000099_fix_blockchainevent_protocolid_index.up.sql
index 4dc3f4ccf9..b2bed6f089 100644
--- a/db/migrations/sqlite/000099_fix_blockchainevent_protocolid_index.up.sql
+++ b/db/migrations/sqlite/000099_fix_blockchainevent_protocolid_index.up.sql
@@ -1,3 +1,5 @@
 DROP INDEX blockchainevents_protocolid;
+DELETE FROM blockchainevents WHERE listener_id IS NULL AND seq NOT IN (
+  SELECT MIN(seq) FROM blockchainevents WHERE listener_id IS NULL GROUP BY namespace, protocol_id);
 CREATE UNIQUE INDEX blockchainevents_protocolid ON blockchainevents(namespace, protocol_id) WHERE listener_id IS NULL;
 CREATE UNIQUE INDEX blockchainevents_listener_protocolid ON blockchainevents(namespace, listener_id, protocol_id) WHERE listener_id IS NOT NULL;