Put the Sprite importer on the default load paths coming from compass.

lib/compass/configuration/adapters.rb

@@ -22,6 +22,8 @@ module Compass
         plugin_opts[:cache] = cache unless cache.nil?
         plugin_opts[:cache_location] = cache_path unless cache_path.nil?
         plugin_opts.merge!(sass_options || {})
+        plugin_opts[:load_paths] ||= []
+        plugin_opts[:load_paths] << Compass::Sprites.new
         plugin_opts
       end
 
@@ -57,6 +59,7 @@ module Compass
           load_paths << framework.stylesheets_directory if File.exists?(framework.stylesheets_directory)
         end
         load_paths += resolve_additional_import_paths
+        load_paths << Compass::Sprites.new
         load_paths
       end
     end

lib/compass/sprites.rb

@@ -102,6 +102,16 @@ module Compass
         File.basename(uri)]
     end
 
+    def mtime(uri, options)
+      Compass.quick_cache("mtime:#{uri}") do
+        self.path, self.name = Compass::Sprites.path_and_name(uri)
+        glob = File.join(Compass.configuration.images_path, uri)
+        Dir.glob(glob).inject(Time.at(0)) do |max_time, file|
+          (t = File.mtime(file)) > max_time ? t : max_time
+        end
+      end
+    end
+    
     def to_s
       ""
     end

spec/sprites_spec.rb

@@ -33,7 +33,6 @@ describe Compass::Sprites do
     options[:line_comments] = false
     options[:style] = :expanded
     options[:syntax] = :scss
-    options[:load_paths] << Compass::Sprites.new
     css = Sass::Engine.new(scss, options).render
     # reformat to fit result of heredoc:
     "      #{css.gsub('@charset "UTF-8";', '').gsub(/\n/, "\n      ").strip}\n"