diff --git a/lib/grape-active_model_serializers.rb b/lib/grape-active_model_serializers.rb
index 0e93c5c..e395587 100644
--- a/lib/grape-active_model_serializers.rb
+++ b/lib/grape-active_model_serializers.rb
@@ -2,4 +2,6 @@ require 'active_model_serializers'
 require 'grape'
 require 'grape-active_model_serializers/endpoint_extension'
 require 'grape-active_model_serializers/formatter'
+require 'grape-active_model_serializers/serializer_resolver'
+require 'grape-active_model_serializers/options_builder'
 require 'grape-active_model_serializers/version'
diff --git a/lib/grape-active_model_serializers/formatter.rb b/lib/grape-active_model_serializers/formatter.rb
index bc97e1b..19b0183 100644
--- a/lib/grape-active_model_serializers/formatter.rb
+++ b/lib/grape-active_model_serializers/formatter.rb
@@ -11,80 +11,20 @@ module Grape
               serializer, options
             ).to_json
           else
-            Grape::Formatter::Json.call resource, env
+            Grape::Formatter::Json.call(resource, env)
           end
         end
 
         def build_options(resource, env)
-          endpoint = env['api.endpoint']
-          options = build_options_from_endpoint(endpoint)
-
-          options[:scope] = endpoint unless options.key?(:scope)
-
-          # ensure we have a root to fallback on
-          if resource.respond_to?(:to_ary) && !options.key?(:root)
-            options[:root] = default_root(endpoint)
-          end
-
-          options.merge(meta_options(env))
+          Grape::ActiveModelSerializers::OptionsBuilder.new(
+            resource, env
+          ).options
         end
 
         def fetch_serializer(resource, options)
-          # use serializer specified by options
-          serializer = options[:serializer]
-
-          if serializer.nil?
-            # fetch serializer leverage AMS lookup
-            serializer = ActiveModel::Serializer.serializer_for(resource)
-            # if grape version exists, attempt to apply version namespacing
-            serializer = namespace_serializer(serializer, options[:version])
-          end
-
-          return nil unless serializer
-
-          serializer.new(resource, options)
-        end
-
-        def namespace_serializer(serializer, namespace)
-          "#{namespace.try(:classify)}::#{serializer}".constantize
-        rescue NameError
-          serializer
-        end
-
-        def meta_options(env)
-          options = {}
-          ams_meta = env['ams_meta'] || {}
-          meta = ams_meta.delete(:meta)
-          meta_key = ams_meta.delete(:meta_key)
-          options[:meta_key] = meta_key if meta && meta_key
-          options[:meta] = meta if meta
-          options
-        end
-
-        def build_options_from_endpoint(endpoint)
-          [
-            endpoint.default_serializer_options || {},
-            endpoint.namespace_options,
-            endpoint.route_options,
-            endpoint.options,
-            endpoint.options.fetch(:route_options)
-          ].reduce(:merge)
-        end
-
-        # array root is the innermost namespace name ('space') if there is one,
-        # otherwise the route name (e.g. get 'name')
-        def default_root(endpoint)
-          innermost_scope = if endpoint.respond_to?(:namespace_stackable)
-                              endpoint.namespace_stackable(:namespace).last
-                            else
-                              endpoint.settings.peek[:namespace]
-                            end
-
-          if innermost_scope
-            innermost_scope.space
-          else
-            endpoint.options[:path][0].to_s.split('/')[-1]
-          end
+          Grape::ActiveModelSerializers::SerializerResolver.new(
+            resource, options
+          ).serializer
         end
       end
     end
diff --git a/lib/grape-active_model_serializers/options_builder.rb b/lib/grape-active_model_serializers/options_builder.rb
new file mode 100644
index 0000000..d7a19c8
--- /dev/null
+++ b/lib/grape-active_model_serializers/options_builder.rb
@@ -0,0 +1,68 @@
+module Grape
+  module ActiveModelSerializers
+    class OptionsBuilder
+      def initialize(resource, env)
+        self.resource = resource
+        self.env = env
+      end
+
+      def options
+        @options ||= (
+          options = endpoint_options
+          options.merge!(scope: endpoint) unless options.key?(:scope)
+          options.merge!(default_root_options) unless options.key?(:root)
+          options.merge!(meta_options)
+          options
+        )
+      end
+
+      private
+
+      attr_accessor :resource, :env
+
+      def endpoint_options
+        [
+          endpoint.default_serializer_options || {},
+          endpoint.namespace_options,
+          endpoint.route_options,
+          endpoint.options,
+          endpoint.options.fetch(:route_options)
+        ].reduce(:merge)
+      end
+
+      def endpoint
+        @endpoint ||= env['api.endpoint']
+      end
+
+      # array root is the innermost namespace name ('space') if there is one,
+      # otherwise the route name (e.g. get 'name')
+      def default_root_options
+        return {} unless resource.respond_to?(:to_ary)
+
+        if innermost_scope
+          { root: innermost_scope.space }
+        else
+          { root: endpoint.options[:path].first.to_s.split('/').last }
+        end
+      end
+
+      def innermost_scope
+        if endpoint.respond_to?(:namespace_stackable)
+          endpoint.namespace_stackable(:namespace).last
+        else
+          endpoint.settings.peek[:namespace]
+        end
+      end
+
+      def meta_options
+        options = {}
+        ams_meta = env['ams_meta'] || {}
+        meta = ams_meta[:meta]
+        meta_key = ams_meta[:meta_key]
+        options[:meta] = meta if meta
+        options[:meta_key] = meta_key if meta && meta_key
+        options
+      end
+    end
+  end
+end
diff --git a/lib/grape-active_model_serializers/serializer_resolver.rb b/lib/grape-active_model_serializers/serializer_resolver.rb
new file mode 100644
index 0000000..e065fb6
--- /dev/null
+++ b/lib/grape-active_model_serializers/serializer_resolver.rb
@@ -0,0 +1,42 @@
+module Grape
+  module ActiveModelSerializers
+    class SerializerResolver
+      def initialize(resource, options)
+        self.resource = resource
+        self.options = options
+      end
+
+      def serializer
+        @serializer ||= (
+          serializer_klass.new(resource, options) if serializer_klass
+        )
+      end
+
+      private
+
+      attr_accessor :resource, :options
+
+      def serializer_klass
+        serializer_klass = options[:serializer]
+        serializer_klass ||= namespaced_resource_serializer_klass
+        serializer_klass
+      end
+
+      def namespaced_resource_serializer_klass
+        "#{namespace}::#{resource_serializer_klass}".constantize
+      rescue NameError
+        resource_serializer_klass
+      end
+
+      def namespace
+        options[:version].try(:classify)
+      end
+
+      def resource_serializer_klass
+        @resource_serializer_klass ||= ActiveModel::Serializer.serializer_for(
+          resource
+        )
+      end
+    end
+  end
+end
diff --git a/spec/grape-active_model_serializers/formatter_spec.rb b/spec/grape-active_model_serializers/formatter_spec.rb
index 4c33296..18ab47b 100644
--- a/spec/grape-active_model_serializers/formatter_spec.rb
+++ b/spec/grape-active_model_serializers/formatter_spec.rb
@@ -18,10 +18,11 @@ describe Grape::Formatter::ActiveModelSerializers do
       end
     end
 
+    let(:env) { { 'api.endpoint' => app.endpoints.first } }
+    let(:options) { described_class.build_options(nil, env) }
+
     it 'should read serializer options like "root"' do
-      expect(
-        described_class.build_options_from_endpoint(app.endpoints.first)
-      ).to include(:root)
+      expect(options).to include(:root)
     end
   end
 
@@ -65,9 +66,7 @@ describe Grape::Formatter::ActiveModelSerializers do
     end
 
     it 'should read serializer options like "root"' do
-      expect(
-        described_class.build_options_from_endpoint(endpoint).keys
-      ).to include(:root)
+      expect(options).to include(:root)
     end
   end
 end
diff --git a/spec/grape-active_model_serializers/versioned_api_formatter_spec.rb b/spec/grape-active_model_serializers/versioned_api_formatter_spec.rb
index 657bb4d..e0bb0b9 100644
--- a/spec/grape-active_model_serializers/versioned_api_formatter_spec.rb
+++ b/spec/grape-active_model_serializers/versioned_api_formatter_spec.rb
@@ -26,10 +26,11 @@ describe Grape::Formatter::ActiveModelSerializers do
         end
       end
 
+      let(:env) { { 'api.endpoint' => app.endpoints.first } }
+      let(:options) { described_class.build_options(nil, env) }
+
       it 'should read serializer options like "root"' do
-        expect(
-          described_class.build_options_from_endpoint(app.endpoints.first)
-        ).to include(:root)
+        expect(options).to include(:root)
       end
     end
 
@@ -72,9 +73,7 @@ describe Grape::Formatter::ActiveModelSerializers do
       end
 
       it 'should read serializer options like "root"' do
-        expect(
-          described_class.build_options_from_endpoint(endpoint).keys
-        ).to include(:root)
+        expect(options).to include(:root)
       end
     end
   end