omg.diff

diff --git a/lib/sprockets/cache_wrapper.rb b/lib/sprockets/cache_wrapper.rb
index 8301e67..c4c9f96 100644
--- a/lib/sprockets/cache_wrapper.rb
+++ b/lib/sprockets/cache_wrapper.rb
@@ -38,21 +38,6 @@ module Sprockets
     end
   end
 
-  class IndexWrapper < CacheWrapper
-    def initialize(*args)
-      @local = {}
-      super
-    end
-
-    def [](key)
-      @local[key] ||= @cache[key]
-    end
-
-    def []=(key, value)
-      @local[key] = @cache[key] = value
-    end
-  end
-
   class GetWrapper < CacheWrapper
     def get(key)
       @cache.get(key)
diff --git a/lib/sprockets/index.rb b/lib/sprockets/index.rb
index d57bf2f..b56c2b4 100644
--- a/lib/sprockets/index.rb
+++ b/lib/sprockets/index.rb
@@ -21,7 +21,7 @@ module Sprockets
       # Copy environment attributes
       @logger            = environment.logger
       @context_class     = environment.context_class
-      @cache             = IndexWrapper.new(self, environment.cache)
+      @cache             = environment.cache.class.new(self, environment.cache)
       @trail             = environment.trail.index
       @digest            = environment.digest
       @digest_class      = environment.digest_class