Exclude extra fee when free shipping

In version 1.2.0 (in a few days) there will be a checkbox, where you can disable the extra fee when free shipping is available.

In the current version (1.1.1) you can use the woocommerce_pay4pay_applyfor_{$current_gateway_id} filter.

This piece of code (best placed in a mu-plugin) should work:

function free_payment_on_free_shipping( $apply_pay4pay ) {
    if ( in_array( 'free_shipping' , WC()->session->get( 'chosen_shipping_methods' ) )
        return false;
    return $apply_pay4pay;
}

    // add filters to every payment method you need
add_filter('woocommerce_pay4pay_applyfor_paypal','free_payment_on_free_shipping');
add_filter('woocommerce_pay4pay_applyfor_[...]','free_payment_on_free_shipping');

This snippet does not work for my. It throws me an error of:
Parse error: syntax error, unexpected ‘return’ (T_RETURN) …
I have WordPress v3.7.1. Woocommerce v2.0.20. and I am working with the version of WooCommerce Pay for Payment 1.0.2 and not I gustria switch to another version.
Could give me some solution?.
Thank you.