How to disable PIV and/or how to disable PIV docs?

I've put:

``` VimL
let loaded_piv = 1
```

in my .vimrc, but when I call

```
:help filetype
```

I get PHP's filetype function description instead of Vim's filetype help.
How can I disable (make disappear) all the docs that PIV contains in the doc directory.
I'm looking for a more elegant/proper solution than deleting the doc directory.
