v1.0.4 > string does not work

I have found a small, non documented, thing in vesion 1.0.4
Sadly I can't upgrade to v2 right now, so I can't test it there.

```
preload :treads # works
preload 'treads' # works not
```

since I am defining certain complex fields dynamically, I actually have a String, and work with `'treads'.to_sym`