diff --git a/resources/migrations/20180419153800-enforce-unique-tx-hash.down.sql b/resources/migrations/20180419153800-enforce-unique-tx-hash.down.sql
new file mode 100644
index 0000000..7f1994f
--- /dev/null
+++ b/resources/migrations/20180419153800-enforce-unique-tx-hash.down.sql
@@ -0,0 +1 @@
+ALTER TABLE issues DROP CONSTRAINT transaction_hash_uniq;
diff --git a/resources/migrations/20180419153800-enforce-unique-tx-hash.up.sql b/resources/migrations/20180419153800-enforce-unique-tx-hash.up.sql
new file mode 100644
index 0000000..ff92e04
--- /dev/null
+++ b/resources/migrations/20180419153800-enforce-unique-tx-hash.up.sql
@@ -0,0 +1 @@
+ALTER TABLE issues ADD CONSTRAINT transaction_hash_uniq UNIQUE (transaction_hash);