diff --git a/lib/active_model/serializer/adapter/json_api.rb b/lib/active_model/serializer/adapter/json_api.rb
index 71327b3c..0d93cac5 100644
--- a/lib/active_model/serializer/adapter/json_api.rb
+++ b/lib/active_model/serializer/adapter/json_api.rb
@@ -8,7 +8,7 @@ module ActiveModel
         end
 
         def serializable_hash(options = {})
-          @root = (options[:root] || serializer.json_key).to_s.pluralize.to_sym
+          @root = (options[:root] || serializer.json_key.to_s.pluralize).to_sym
           @hash = {}
 
           if serializer.respond_to?(:each)
diff --git a/test/action_controller/serialization_test.rb b/test/action_controller/serialization_test.rb
index 4103e273..fbbb48f9 100644
--- a/test/action_controller/serialization_test.rb
+++ b/test/action_controller/serialization_test.rb
@@ -24,6 +24,16 @@ module ActionController
           ActiveModel::Serializer.config.adapter = old_adapter
         end
 
+        def render_using_custom_root_in_adapter_with_a_default
+          old_adapter = ActiveModel::Serializer.config.adapter
+          # JSON-API adapter sets root by default
+          ActiveModel::Serializer.config.adapter = ActiveModel::Serializer::Adapter::JsonApi
+          @profile = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
+          render json: @profile, root: "profile"
+        ensure
+          ActiveModel::Serializer.config.adapter = old_adapter
+        end
+
         def render_array_using_implicit_serializer
           array = [
             Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' }),
@@ -57,6 +67,13 @@ module ActionController
         assert_equal '{"profiles":{"name":"Name 1","description":"Description 1"}}', @response.body
       end
 
+      def test_render_using_custom_root_in_adapter_with_a_default
+        get :render_using_custom_root_in_adapter_with_a_default
+
+        assert_equal 'application/json', @response.content_type
+        assert_equal '{"profile":{"name":"Name 1","description":"Description 1"}}', @response.body
+      end
+
       def test_render_array_using_implicit_serializer
         get :render_array_using_implicit_serializer
         assert_equal 'application/json', @response.content_type