Flutter arb file spacing in a select translation

Question

I am trying to translate a list of countries like that:

arb file:

"countries": "{choice, select, United States {United States} Mexico {Mexico} other {None}}",

The implementation should be like this:

S.of(context).countries(countryName)

but the issue is it's not detecting two words as a single key when S.of(context).countries('United States')

The problem is with the 2 words countries or whatever.