diff --git a/transaction.go b/transaction.go
index 204d9624c..154faa227 100644
--- a/transaction.go
+++ b/transaction.go
@@ -4,6 +4,7 @@ package gosnowflake
 
 import (
 	"database/sql/driver"
+	"errors"
 )
 
 type snowflakeTx struct {
@@ -17,8 +18,14 @@ const (
 	rollback
 )
 
-func (cmd txCommand) string() string {
-	return [...]string{"COMMIT", "ROLLBACK"}[cmd]
+func (cmd txCommand) string() (txStr string, err error) {
+	switch cmd {
+	case commit:
+		return "COMMIT", nil
+	case rollback:
+		return "ROLLBACK", nil
+	}
+	return "", errors.New("unsupported transaction command")
 }
 
 func (tx *snowflakeTx) Commit() (err error) {
@@ -30,10 +37,14 @@ func (tx *snowflakeTx) Rollback() (err error) {
 }
 
 func (tx *snowflakeTx) execTxCommand(command txCommand) (err error) {
+	txStr, err := command.string()
+	if err != nil {
+		return err
+	}
 	if tx.sc == nil || tx.sc.rest == nil {
 		return driver.ErrBadConn
 	}
-	_, err = tx.sc.exec(tx.sc.ctx, command.string(), false /* noResult */, false /* isInternal */, false /* describeOnly */, nil)
+	_, err = tx.sc.exec(tx.sc.ctx, txStr, false /* noResult */, false /* isInternal */, false /* describeOnly */, nil)
 	if err != nil {
 		return
 	}