diff --git a/store/cmd_hist.go b/store/cmd_hist.go
index d62cae66..c1754a3c 100644
--- a/store/cmd_hist.go
+++ b/store/cmd_hist.go
@@ -21,14 +21,17 @@ func init() {
 
 func addLastAmongDup(tx *sql.Tx) error {
 	// Upgrade from early version where lastAmongDup is missing.
-	rows, err := tx.Query("pragma table_info(cmd)")
+	rows, err := tx.Query("select * from cmd limit 1")
 	if err != nil {
 		return err
 	}
+	defer rows.Close()
+
 	hasLastAmongDup, err := hasColumn(rows, "lastAmongDup")
 	if err != nil {
 		return err
 	}
+
 	if !hasLastAmongDup {
 		_, err := tx.Exec("alter table cmd add column lastAmongDup bool")
 		if err != nil {
@@ -39,7 +42,7 @@ func addLastAmongDup(tx *sql.Tx) error {
 			return err
 		}
 	}
-	return tx.Commit()
+	return nil
 }
 
 // NextCmdSeq returns the next sequence number of the command history.
diff --git a/store/sqlutil.go b/store/sqlutil.go
index ff9a934f..e612ba0d 100644
--- a/store/sqlutil.go
+++ b/store/sqlutil.go
@@ -7,19 +7,8 @@ func hasColumn(rows *sql.Rows, colname string) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	dests := make([]interface{}, len(cols))
-	var name string
-	for i, col := range cols {
-		if col == "name" {
-			dests[i] = &name
-		} else {
-			dests[i] = new(interface{})
-		}
-	}
-	defer rows.Close()
-	for rows.Next() {
-		rows.Scan(dests...)
-		if name == colname {
+	for _, col := range cols {
+		if col == colname {
 			return true, nil
 		}
 	}
@@ -35,9 +24,9 @@ func transaction(db *sql.DB, f func(*sql.Tx) error) error {
 	}
 	err = f(tx)
 	if err != nil {
-		tx.Rollback()
+		return tx.Rollback()
 	} else {
-		tx.Commit()
+		return tx.Commit()
 	}
 	return err
 }