object not renaming

I set "Transform Object Keys" to true.
input 
```
function tes() {
  return { 'key': 'val' }
}
```
output

```
function _0x331670() {
    return { 'key': '\x76\x61\x6c' };
}
```

it should be like this or not?
```
function _0x331670() {
    return { '\x6b\x65\x79': '\x76\x61\x6c' };
}
```