<header class="admin-nav-header">
  <%= link_to spree.admin_path do %>
    <%= image_tag(Spree::Config[:admin_interface_logo]) %>
  <%- end %>
</header>

<header class="admin-nav-header">
  <%= link_to spree.admin_path, class: 'brand-link' do %>
    <%= image_tag(Spree::Config[:admin_interface_logo]) %>
  <%- end %>
</header>

Put back class on admin logo
Put back class on admin logo

  - available for replace by Deface overrides

  - as well pointed out by @tvdeyen
