Could not parse knowledge when using 'not contains' in a parentheses leading a '!'

This code could not be parsed correctly:

rule "out"
when
Msg(!(set not contains "test"))
then
end

I tried a few simple situations and found that when using 'not contains' operator in a '!' leading parentheses triggers this problem. If no '!' prefixing the parentheses,the program works like a charm...

The example above seemed so stupid(you can use a 'contains' operator instead), but this is the simplest toy example.And this problem would be looked more important if you want to write some logic like this:

Msg(!(set not contains "test" || !bool && string == "hello"))