# File lib/compass/commands/update_project.rb, line 53
      def new_compiler_instance(additional_options = {})
        @compiler_opts ||= begin
          compiler_opts = {:sass => Compass.sass_engine_options}
          compiler_opts.merge!(options)
          compiler_opts[:sass_files] = explicit_sass_files
          compiler_opts[:cache_location] = determine_cache_location
          compiler_opts
        end

        @memory_store ||= Sass::CacheStores::Memory.new
        @backing_store ||= compiler_opts[:cache_store]
        @backing_store ||= Sass::CacheStores::Filesystem.new(determine_cache_location)
        @cache_store ||= Sass::CacheStores::Chain.new(@memory_store, @backing_store)
        @memory_store.reset!

        Compass::Compiler.new(
          working_path,
          Compass.configuration.sass_path,
          Compass.configuration.css_path,
          @compiler_opts.merge(:cache_store => @cache_store).merge(additional_options)
        )
      end