base_url in different Behat profiles not respected

[lnhrdt]

With a behat.yml configuration file such as the one below, when running profile_a the base_url is not used -- the tests run on URL_A.

default:
    extensions:
        page_object_extension.phar: ~
        Behat\MinkExtension\Extension:
            goutte: ~
            selenium2: ~
            base_url: URL_A
            default_session: selenium2
            browser_name: 'firefox'
        shvetsgroup\ParallelRunner\Extension: ~
profile_a:
    extensions:
        Behat\MinkExtension\Extension:
            base_url: URL_B
            browser_name: 'firefox'
        shvetsgroup\ParallelRunner\Extension:
            process_count: 4