diff --git a/lib/active_model/serializer/adapter.rb b/lib/active_model/serializer/adapter.rb
index bc658ba2..b8e6bbcd 100644
--- a/lib/active_model/serializer/adapter.rb
+++ b/lib/active_model/serializer/adapter.rb
@@ -48,7 +48,7 @@ module ActiveModel
             yield
           end
         elsif is_fragment_cached?
-          FragmentCache.new(self, @cached_serializer, @options, @root).fetch
+          FragmentCache.new(self, @cached_serializer, @options).fetch
         else
           yield
         end
diff --git a/lib/active_model/serializer/adapter/fragment_cache.rb b/lib/active_model/serializer/adapter/fragment_cache.rb
index 2b7596a4..231ddaed 100644
--- a/lib/active_model/serializer/adapter/fragment_cache.rb
+++ b/lib/active_model/serializer/adapter/fragment_cache.rb
@@ -5,8 +5,7 @@ module ActiveModel
 
         attr_reader :serializer
 
-        def initialize(adapter, serializer, options, root)
-          @root       = root
+        def initialize(adapter, serializer, options)
           @options    = options
           @adapter    = adapter
           @serializer = serializer
diff --git a/test/adapter/fragment_cache_test.rb b/test/adapter/fragment_cache_test.rb
index 69303557..d249637a 100644
--- a/test/adapter/fragment_cache_test.rb
+++ b/test/adapter/fragment_cache_test.rb
@@ -8,7 +8,7 @@ module ActiveModel
           @role            = Role.new(name: 'Great Author', description:nil)
           @role.author     = [@author]
           @role_serializer = RoleSerializer.new(@role)
-          @role_hash       = FragmentCache.new(RoleSerializer.adapter.new(@role_serializer), @role_serializer, {}, nil)
+          @role_hash       = FragmentCache.new(RoleSerializer.adapter.new(@role_serializer), @role_serializer, {})
         end
 
         def test_fragment_fetch_with_virtual_attributes