diff --git a/crates/erc20_payment_lib_common/migrations/20240320000001_add_idx.sql b/crates/erc20_payment_lib_common/migrations/20240320000001_add_idx.sql
index 5d682d38..84bb17d9 100644
--- a/crates/erc20_payment_lib_common/migrations/20240320000001_add_idx.sql
+++ b/crates/erc20_payment_lib_common/migrations/20240320000001_add_idx.sql
@@ -1,2 +1,2 @@
 DROP INDEX "idx_chain_tx_tx_hash";
-CREATE INDEX "idx_chain_tx_tx_hash" ON "chain_tx" ("tx_hash");
+CREATE UNIQUE INDEX "idx_chain_tx_tx_hash" ON "chain_tx" ("tx_hash");