diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..d48d370
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+2.6.9
diff --git a/lib/jsonapi/filtering.rb b/lib/jsonapi/filtering.rb
index 70d47db..018fda6 100644
--- a/lib/jsonapi/filtering.rb
+++ b/lib/jsonapi/filtering.rb
@@ -8,16 +8,19 @@ module Filtering
     #
     # @param requested_field [String] the field to parse
     # @return [Array] with the fields and the predicate
-    def self.extract_attributes_and_predicates(requested_field)
+    def self.extract_attributes_and_predicates(requested_field, allowed_fields)
       predicates = []
       field_name = requested_field.to_s.dup
 
       while Ransack::Predicate.detect_from_string(field_name).present? do
+        # break if we have an exect match with an allowed_fields
+        # we do not want to pick apart the string further
+        break if allowed_fields.include?(field_name)
+
         predicate = Ransack::Predicate
           .detect_and_strip_from_string!(field_name)
         predicates << Ransack::Predicate.named(predicate)
       end
-
       [field_name.split(/_and_|_or_/), predicates.reverse]
     end
 
@@ -32,9 +35,11 @@ def self.extract_attributes_and_predicates(requested_field)
     # @param allowed_fields [Array] a list of allowed fields to be filtered
     # @param options [Hash] extra flags to enable/disable features
     # @return [ActiveRecord::Base] a collection of resources
-    def jsonapi_filter(resources, allowed_fields, options = {})
+    def jsonapi_filter(resources, allowed_fields, *allowed_scopes, options)
+      options = options || {}
+      allowed_scopes = (allowed_scopes || []).flatten.map(&:to_s)
       allowed_fields = allowed_fields.map(&:to_s)
-      extracted_params = jsonapi_filter_params(allowed_fields)
+      extracted_params = jsonapi_filter_params(allowed_fields, allowed_scopes)
       extracted_params[:sorts] = jsonapi_sort_params(allowed_fields, options)
       resources = resources.ransack(extracted_params)
       block_given? ? yield(resources) : resources
@@ -47,14 +52,14 @@ def jsonapi_filter(resources, allowed_fields, options = {})
     #
     # @param allowed_fields [Array] a list of allowed fields to be filtered
     # @return [Hash] to be passed to [ActiveRecord::Base#order]
-    def jsonapi_filter_params(allowed_fields)
+    def jsonapi_filter_params(allowed_fields, allowed_scopes)
       filtered = {}
       requested = params[:filter] || {}
       allowed_fields = allowed_fields.map(&:to_s)
 
       requested.each_pair do |requested_field, to_filter|
         field_names, predicates = JSONAPI::Filtering
-          .extract_attributes_and_predicates(requested_field)
+          .extract_attributes_and_predicates(requested_field, allowed_fields)
 
         wants_array = predicates.any? && predicates.map(&:wants_array).any?
 
@@ -62,6 +67,20 @@ def jsonapi_filter_params(allowed_fields)
           to_filter = to_filter.split(',')
         end
 
+        # filter by scopes expects an exact match
+        # with the `allowed_scopes`. Predicates can be a part of named scopes
+        # and should be handled first
+        # Make sure to move to the next after a match
+        # {"created_before"=>"2013-02-01"}
+        # {"created_before_gt"=>"2013-02-01"}
+        if allowed_scopes.include?(requested_field)
+          filtered[requested_field] = to_filter
+          next
+        end
+
+
+        # filter by attributes
+        # {"first_name_eq"=>"Beau"}
         if predicates.any? && (field_names - allowed_fields).empty?
           filtered[requested_field] = to_filter
         end
@@ -88,7 +107,7 @@ def jsonapi_sort_params(allowed_fields, options = {})
         end
 
         field_names, predicates = JSONAPI::Filtering
-          .extract_attributes_and_predicates(requested_field)
+          .extract_attributes_and_predicates(requested_field, allowed_fields)
 
         next unless (field_names - allowed_fields).empty?
         next if !options[:sort_with_expressions] && predicates.any?
diff --git a/lib/jsonapi/rails.rb b/lib/jsonapi/rails.rb
index 8d29d17..c221268 100644
--- a/lib/jsonapi/rails.rb
+++ b/lib/jsonapi/rails.rb
@@ -37,7 +37,7 @@ def self.install!
     # @return [NilClass]
     def self.add_errors_renderer!
       ActionController::Renderers.add(:jsonapi_errors) do |resource, options|
-        self.content_type ||= Mime[:jsonapi]
+        self.content_type = Mime[:jsonapi] if self.media_type.nil?
 
         many = JSONAPI::Rails.is_collection?(resource, options[:is_collection])
         resource = [resource] unless many
@@ -47,7 +47,7 @@ def self.add_errors_renderer!
         ) unless resource.is_a?(ActiveModel::Errors)
 
         errors = []
-        model = resource.instance_variable_get('@base')
+        model = resource.instance_variable_get(:@base)
 
         if respond_to?(:jsonapi_serializer_class, true)
           model_serializer = jsonapi_serializer_class(model, false)
@@ -90,7 +90,7 @@ def self.add_errors_renderer!
     # @return [NilClass]
     def self.add_renderer!
       ActionController::Renderers.add(:jsonapi) do |resource, options|
-        self.content_type ||= Mime[:jsonapi]
+        self.content_type = Mime[:jsonapi] if self.media_type.nil?
 
         JSONAPI_METHODS_MAPPING.to_a[0..1].each do |opt, method_name|
           next unless respond_to?(method_name, true)
diff --git a/spec/dummy.rb b/spec/dummy.rb
index 6f0c434..d273f81 100644
--- a/spec/dummy.rb
+++ b/spec/dummy.rb
@@ -18,6 +18,7 @@
   create_table :users, force: true do |t|
     t.string :first_name
     t.string :last_name
+    t.integer :notes_count, default: 0
     t.timestamps
   end
 
@@ -31,6 +32,11 @@
 
 class User < ActiveRecord::Base
   has_many :notes
+  scope :created_before, ->(date) { where('created_at < ?', date) }
+
+  def self.ransackable_scopes(auth_object = nil)
+    %i(created_before)
+  end
 end
 
 class Note < ActiveRecord::Base
@@ -83,11 +89,18 @@ class UsersController < ActionController::Base
   def index
     allowed_fields = [
       :first_name, :last_name, :created_at,
-      :notes_created_at, :notes_quantity
+      :notes_created_at, :notes_quantity,
+      :notes_count
+    ]
+    allowed_scopes = [
+      :created_before
     ]
     options = { sort_with_expressions: true }
 
-    jsonapi_filter(User.all, allowed_fields, options) do |filtered|
+    jsonapi_filter(User.all,
+                   allowed_fields,
+                   allowed_scopes,
+                   options) do |filtered|
       result = filtered.result
 
       if params[:sort].to_s.include?('notes_quantity')
diff --git a/spec/errors_spec.rb b/spec/errors_spec.rb
index da3d0f5..38cf978 100644
--- a/spec/errors_spec.rb
+++ b/spec/errors_spec.rb
@@ -31,6 +31,7 @@
 
       it do
         expect(response).to have_http_status(:unprocessable_entity)
+        expect(response.media_type).to eq('application/vnd.api+json')
         expect(response_json['errors'].size).to eq(1)
         expect(response_json['errors'][0]['status']).to eq('422')
         expect(response_json['errors'][0]['title'])
diff --git a/spec/fetching_spec.rb b/spec/fetching_spec.rb
index a5382e7..513f185 100644
--- a/spec/fetching_spec.rb
+++ b/spec/fetching_spec.rb
@@ -25,6 +25,7 @@
         it do
           expect(response).to have_http_status(:ok)
           expect(response_json['data'].size).to eq(users.size)
+          expect(response.media_type).to eq('application/vnd.api+json')
 
           response_json['data'].each do |item|
             user = users.detect { |u| u.id == item['id'].to_i }
diff --git a/spec/filtering_spec.rb b/spec/filtering_spec.rb
index f3bd80a..ce43907 100644
--- a/spec/filtering_spec.rb
+++ b/spec/filtering_spec.rb
@@ -4,18 +4,31 @@
   describe '#extract_attributes_and_predicate' do
     context 'mixed attributes (and/or)' do
       it 'extracts ANDs' do
-        attributes, predicates = JSONAPI::Filtering
-          .extract_attributes_and_predicates('attr1_and_attr2_eq')
+        attributes, predicates =
+          JSONAPI::Filtering.extract_attributes_and_predicates(
+            'attr1_and_attr2_eq',
+            ['attr1', 'attr2']
+          )
         expect(attributes).to eq(['attr1', 'attr2'])
         expect(predicates.size).to eq(1)
         expect(predicates[0].name).to eq('eq')
       end
     end
 
+    context 'handle attributes with underscore in name' do
+      it 'detect _' do
+        attributes, predicates = JSONAPI::Filtering
+          .extract_attributes_and_predicates('notes_count_eq', ['notes_count'])
+        expect(attributes).to eq(['notes_count'])
+        expect(predicates.size).to eq(1)
+        expect(predicates[0].name).to eq('eq')
+      end
+    end
+
     context 'mixed predicates' do
       it 'extracts in order' do
         attributes, predicates = JSONAPI::Filtering
-          .extract_attributes_and_predicates('attr1_sum_eq')
+          .extract_attributes_and_predicates('attr1_sum_eq', ['attr1'])
         expect(attributes).to eq(['attr1'])
         expect(predicates.size).to eq(2)
         expect(predicates[0].name).to eq('sum')
@@ -85,6 +98,32 @@
         end
       end
 
+      context 'returns users by counter_cache' do
+        let(:params) do
+          second_user.update(notes_count: 1)
+          {
+            filter: { notes_count_eq: 1 }
+          }
+        end
+
+        it 'ensures ransack scopes work properly' do
+          ransack = User.ransack(notes_count_eq: 1)
+          expected_sql = 'SELECT "users".* FROM "users" WHERE '\
+                         '"users"."notes_count" = 1'
+          expect(ransack.result.to_sql).to eq(expected_sql)
+        end
+
+        it do
+          expect(first_user.notes_count).to eq(0)
+          expect(second_user.notes_count).to eq(1)
+          expect(third_user.notes_count).to eq(0)
+
+          expect(response).to have_http_status(:ok)
+          expect(response_json['data'].size).to eq(1)
+          expect(response_json['data'][0]).to have_id(second_user.id.to_s)
+        end
+      end
+
       context 'returns sorted users by notes' do
         let(:params) do
           { sort: '-notes_created_at' }
@@ -96,6 +135,29 @@
           expect(response_json['data'][0]).to have_id(second_user.id.to_s)
         end
       end
+
+      context 'returns users filtered by scope' do
+        let(:params) do
+          third_user.update(created_at: '2013-01-01')
+
+          {
+            filter: { created_before: '2013-02-01' }
+          }
+        end
+
+        it 'ensures ransack scopes are working properly' do
+          ransack = User.ransack({ created_before: '2013-02-01' })
+          expected_sql = 'SELECT "users".* FROM "users" WHERE '\
+                         '(created_at < \'2013-02-01\')'
+          expect(ransack.result.to_sql).to eq(expected_sql)
+        end
+
+        it 'should return only' do
+          expect(response).to have_http_status(:ok)
+          expect(response_json['data'].size).to eq(1)
+          expect(response_json['data'][0]).to have_id(third_user.id.to_s)
+        end
+      end
     end
   end
 end