Complex (a bit) expressions in filters?

I'm trying to use crop with min, and I'm getting exception.

This fails:
`-filter:v crop=iw:min(iw,ih)`

With the error:
```
[fferr] [NULL @ 0x1a6bc00] Unable to find a suitable output format for 'ih))"'
```

Note that this works:
`-filter:v crop=iw:ih`


Is there a quick fix? perhaps some escape/quotes I'm missing?
