diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 032f0fb9c1..6551be01f9 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *Edge*
 
+* Allow MemCacheStore to be initialized with a MemCache object instead of addresses and options [Bryan Helmkamp]
+
 * Change spelling of Kyev timezone to Kyiv #2613 [Alexander Dymo]
 
 * Add ActiveSupport.parse_json_times to disable time parsing in JSON backends that don't support it or don't need it. [rick]
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index 90b7526fe1..ab8eb72096 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -23,7 +23,12 @@ module ActiveSupport
         DELETED     = "DELETED\r\n"
       end
 
-      attr_reader :addresses
+      def self.build_mem_cache(*addresses)
+        addresses = addresses.flatten
+        options = addresses.extract_options!
+        addresses = ["localhost"] if addresses.empty?
+        MemCache.new(addresses, options)
+      end
 
       # Creates a new MemCacheStore object, with the given memcached server
       # addresses. Each address is either a host name, or a host-with-port string
@@ -34,11 +39,11 @@ module ActiveSupport
       # If no addresses are specified, then MemCacheStore will connect to
       # localhost port 11211 (the default memcached port).
       def initialize(*addresses)
-        addresses = addresses.flatten
-        options = addresses.extract_options!
-        addresses = ["localhost"] if addresses.empty?
-        @addresses = addresses
-        @data = MemCache.new(addresses, options)
+        if addresses.first.is_a?(MemCache)
+          @data = addresses.first
+        else
+          @data = self.class.build_mem_cache(*addresses)
+        end
 
         extend Strategy::LocalCache
       end
diff --git a/activesupport/test/caching_test.rb b/activesupport/test/caching_test.rb
index b845796fe5..ad19dcfd09 100644
--- a/activesupport/test/caching_test.rb
+++ b/activesupport/test/caching_test.rb
@@ -15,22 +15,28 @@ class CacheStoreSettingTest < ActiveSupport::TestCase
   end
 
   def test_mem_cache_fragment_cache_store
+    MemCache.expects(:new).with(%w[localhost], {})
     store = ActiveSupport::Cache.lookup_store :mem_cache_store, "localhost"
     assert_kind_of(ActiveSupport::Cache::MemCacheStore, store)
-    assert_equal %w(localhost), store.addresses
+  end
+
+  def test_mem_cache_fragment_cache_store_with_given_mem_cache
+    mem_cache = MemCache.new
+    MemCache.expects(:new).never
+    store = ActiveSupport::Cache.lookup_store :mem_cache_store, mem_cache
+    assert_kind_of(ActiveSupport::Cache::MemCacheStore, store)
   end
 
   def test_mem_cache_fragment_cache_store_with_multiple_servers
+    MemCache.expects(:new).with(%w[localhost 192.168.1.1], {})
     store = ActiveSupport::Cache.lookup_store :mem_cache_store, "localhost", '192.168.1.1'
     assert_kind_of(ActiveSupport::Cache::MemCacheStore, store)
-    assert_equal %w(localhost 192.168.1.1), store.addresses
   end
 
   def test_mem_cache_fragment_cache_store_with_options
+    MemCache.expects(:new).with(%w[localhost 192.168.1.1], { :namespace => "foo" })
     store = ActiveSupport::Cache.lookup_store :mem_cache_store, "localhost", '192.168.1.1', :namespace => 'foo'
     assert_kind_of(ActiveSupport::Cache::MemCacheStore, store)
-    assert_equal %w(localhost 192.168.1.1), store.addresses
-    assert_equal 'foo', store.instance_variable_get('@data').instance_variable_get('@namespace')
   end
 
   def test_object_assigned_fragment_cache_store