Does remove immutability using cast to pass in a function make sense?

[AsmMan via Digitalmars-d-learn]

I have this array:

static immutable string[] months = ["jan", "fev", ...];
I need to pass it into canFind(). But it doesn't works with 
immutables so I need to cast it like in canFind(cast(string[]) 
months, month) to work. There's a reason related to design why it 
doesn't work with immutables or a function just wasn't written?

What I want to know is if I'm doing something wrong in casting it 
to work. I know from C which such casts should be done carefully