capistrano if statement/variable check does not work

I have the simple deployment script as below, in console, stage is printed as "staging", but the error is not shown. Is the if check wrong? Thanks for help!

namespace :deploy do
    task :check do
    print stage
    if (stage == "staging")
        raise "Please do not deploy non-master branch to staging or production, try multistage!"
    end
end