spree 2-4 core dependency issue

[shoaib-iqbal]

gem 'spree', github: 'spree/spree', branch: '2-4-stable'
gem 'spree_active_shipping', :git => "git://github.com/spree/spree_active_shipping", :branch => "2-4-stable"
rails 4.1.8
ruby 2.1.1

Bundler could not find compatible versions for gem "spree_core":
  In snapshot (Gemfile.lock):
    spree_core (= 2.4.3.beta)

  In Gemfile:
    spree_active_shipping was resolved to 2.4.0, which depends on
      spree_core (~> 2.4.3)

    spree_social_products was resolved to 2.0, which depends on
      spree_core (~> 2.4.0)

`