Selenium : PHP Fatal error: Call to a member function elements() on null

My behat test run fine in Drupal 7 (selenium and chrome )but with similar settings in behat.yml Selenium gives the following error in Drupal 8.

PHP Fatal error: Call to a member function elements() on null in /Users/xyz/Sites/abc/vendor/behat/mink-selenium2-driver/src/Selenium2Driver.php on line 488