diff --git a/backend/internal/database/migrate.go b/backend/internal/database/migrate.go
index cb158521..fabc4d3b 100644
--- a/backend/internal/database/migrate.go
+++ b/backend/internal/database/migrate.go
@@ -116,6 +116,10 @@ func MigrateSteps(dbURL string, migrationsPath string, steps int) error {
 
 // RollbackMigrations rolls back all migrations (drops all tables).
 func RollbackMigrations(dbURL string, migrationsPath string) error {
+	if migrationsPath == "" {
+		return errors.New("migrations path is required")
+	}
+
 	m, err := migrate.New(
 		fmt.Sprintf("file://%s", migrationsPath),
 		dbURL,
diff --git a/backend/internal/repository/captain_inbox_repo_test.go b/backend/internal/repository/captain_inbox_repo_test.go
index e19b5312..406c89ab 100644
--- a/backend/internal/repository/captain_inbox_repo_test.go
+++ b/backend/internal/repository/captain_inbox_repo_test.go
@@ -34,6 +34,17 @@ func TestCaptainInboxRepo_Create(t *testing.T) {
 	assert.Equal(t, uint(100), ci.AccountID)
 }
 
+func TestCaptainInboxRepo_Create_OnlyOneActiveAssistantPerInbox(t *testing.T) {
+	db := setupTestDB(t, &model.CaptainInbox{})
+	repo := NewCaptainInboxRepo(db)
+	ctx := context.Background()
+
+	require.NoError(t, repo.Create(ctx, newTestCaptainInbox(1, 10, 100)))
+	require.Error(t, repo.Create(ctx, newTestCaptainInbox(2, 10, 100)))
+	require.NoError(t, repo.Delete(ctx, 1, 10))
+	require.NoError(t, repo.Create(ctx, newTestCaptainInbox(2, 10, 100)))
+}
+
 // ========== Delete ==========
 
 func TestCaptainInboxRepo_Delete(t *testing.T) {