diff --git a/src/migrations/20251013131405-milestone-progression-uniqueness.js b/src/migrations/20251013131405-milestone-progression-uniqueness.js
new file mode 100644
index 0000000000..0779dcead2
--- /dev/null
+++ b/src/migrations/20251013131405-milestone-progression-uniqueness.js
@@ -0,0 +1,14 @@
+exports.up = function(db, cb) {
+    db.runSql(
+        `DROP INDEX IF EXISTS milestone_progressions_source_milestone_idx;
+         CREATE UNIQUE INDEX milestone_progressions_source_milestone_idx ON milestone_progressions(source_milestone);`,
+        cb,
+    );
+};
+
+exports.down = function(db, cb) {
+    db.runSql(
+        `DROP INDEX IF EXISTS milestone_progressions_source_milestone_idx;`,
+        cb,
+    );
+};