diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 83021bf3dd..e0d6a1673b 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1,19 +1,19 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2017-06-12 13:25:24 -0600 using RuboCop version 0.47.0.
+# on 2017-06-13 12:09:49 -0400 using RuboCop version 0.47.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
 
-# Offense count: 44
+# Offense count: 45
 Metrics/AbcSize:
   Max: 44
 
-# Offense count: 277
+# Offense count: 278
 # Configuration parameters: CountComments, ExcludedMethods.
 Metrics/BlockLength:
-  Max: 3104
+  Max: 3117
 
 # Offense count: 8
 # Configuration parameters: CountComments.
@@ -24,7 +24,7 @@ Metrics/ClassLength:
 Metrics/CyclomaticComplexity:
   Max: 14
 
-# Offense count: 1098
+# Offense count: 1108
 # Configuration parameters: AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
 # URISchemes: http, https
 Metrics/LineLength:
diff --git a/.travis.yml b/.travis.yml
index ca11c73be0..342dc0e3b7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,6 +17,16 @@ matrix:
       gemfile: gemfiles/rails_edge.gemfile
     - rvm: 2.4.1
       gemfile: gemfiles/rails_5.gemfile
+    - rvm: 2.4.1
+      gemfile: gemfiles/multi_json.gemfile
+      script:
+        - bundle exec rake
+        - bundle exec rspec spec/integration/multi_json
+    - rvm: 2.4.1
+      gemfile: gemfiles/multi_xml.gemfile
+      script:
+        - bundle exec rake
+        - bundle exec rspec spec/integration/multi_xml
     - rvm: 2.3.4
       gemfile: Gemfile
     - rvm: 2.3.4
diff --git a/Appraisals b/Appraisals
index eb5efc247f..5ceb072bc0 100644
--- a/Appraisals
+++ b/Appraisals
@@ -22,3 +22,11 @@ end
 appraise 'rack-edge' do
   gem 'rack', github: 'rack/rack'
 end
+
+appraise 'multi_json' do
+  gem 'multi_json', require: 'multi_json'
+end
+
+appraise 'multi_xml' do
+  gem 'multi_xml', require: 'multi_xml'
+end
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c32b748c0..236b2fa5ac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 * [#1622](https://github.com/ruby-grape/grape/pull/1622): Add `except_values` validator to replace `except` option of `values` validator - [@jlfaber](https://github.com/jlfaber).
 * [#1635](https://github.com/ruby-grape/grape/pull/1635): Instrument validators with ActiveSupport::Notifications - [@ktimothy](https://github.com/ktimothy).
 * [#1646](https://github.com/ruby-grape/grape/pull/1646): Add ability to include an array of modules as helpers - [@pablonahuelgomez](https://github.com/pablonahuelgomez).
+* [#1623](https://github.com/ruby-grape/grape/pull/1623): Removed `multi_json` and `multi_xml` dependencies - [@dblock](https://github.com/dblock).
 * Your contribution here.
 
 #### Fixes
diff --git a/README.md b/README.md
index a3cc7bfc41..3ecf5a7c17 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,7 @@
   - [CORS](#cors)
 - [Content-type](#content-type)
 - [API Data Formats](#api-data-formats)
+- [JSON and XML Processors](#json-and-xml-processors)
 - [RESTful Model Representations](#restful-model-representations)
   - [Grape Entities](#grape-entities)
   - [Hypermedia and Roar](#hypermedia-and-roar)
@@ -1146,7 +1147,7 @@ end
 ```
 
 The `:values` option can also be supplied with a `Proc`, evaluated lazily with each request.
-If the Proc has arity zero (i.e. it takes no arguments) it is expected to return either a list 
+If the Proc has arity zero (i.e. it takes no arguments) it is expected to return either a list
 or a range which will then be used to validate the parameter.
 
 For example, given a status model you may want to restrict by hashtags that you have
@@ -2564,6 +2565,10 @@ curl -X PUT -d 'data' 'http://localhost:9292/value' -H Content-Type:text/custom
 
 You can disable parsing for a content-type with `nil`. For example, `parser :json, nil` will disable JSON parsing altogether. The request data is then available as-is in `env['api.request.body']`.
 
+## JSON and XML Processors
+
+Grape uses `JSON` and `ActiveSupport::XmlMini` for JSON and XML parsing by default. It also detects and supports [multi_json](https://github.com/intridea/multi_json) and [multi_xml](https://github.com/sferik/multi_xml). Adding those gems to your Gemfile and requiring them will enable them and allow you to swap the JSON and XML back-ends.
+
 ## RESTful Model Representations
 
 Grape supports a range of ways to present your data with some help from a generic `present` method,
diff --git a/Rakefile b/Rakefile
index f4e330c030..1df4278400 100644
--- a/Rakefile
+++ b/Rakefile
@@ -7,6 +7,7 @@ Bundler::GemHelper.install_tasks
 require 'rspec/core/rake_task'
 RSpec::Core::RakeTask.new(:spec) do |spec|
   spec.pattern = 'spec/**/*_spec.rb'
+  spec.exclude_pattern = 'spec/integration/**/*_spec.rb'
 end
 
 RSpec::Core::RakeTask.new(:rcov) do |spec|
diff --git a/UPGRADING.md b/UPGRADING.md
index c26b9588d3..41cd80eb40 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -3,6 +3,16 @@ Upgrading Grape
 
 ### Upgrading to >= 1.0.0
 
+#### Changes in XML and JSON Parsers
+
+Grape no longer uses `multi_json` or `multi_xml` by default and uses `JSON` and `ActiveSupport::XmlMini` instead. This has no visible impact on JSON processing, but the default behavior of the XML parser has changed. For example, an XML POST containing `<user>Bobby T.</user>` was parsed as `Bobby T.` with `multi_xml`, and as now parsed as `{"__content__"=>"Bobby T."}` with `XmlMini`.
+
+If you were using `MultiJson.load`, `MultiJson.dump` or `MultiXml.parse`, you can substitute those with `Grape::Json.load`, `Grape::Json.dump`, `::Grape::Xml.parse`, or directly with `JSON.load`, `JSON.dump`, `XmlMini.parse`, etc.
+
+To restore previous behavior, add `multi_json` or `multi_xml` to your `Gemfile` and `require` it.
+
+See [#1623](https://github.com/ruby-grape/grape/pull/1623) for more information.
+
 #### Changes in Parameter Class
 
 The default class for `params` has changed from `Hashie::Mash` to `ActiveSupport::HashWithIndifferentAccess` and the `hashie` dependency has been removed. This means that by default you can no longer access parameters by method name.
diff --git a/gemfiles/multi_json.gemfile b/gemfiles/multi_json.gemfile
new file mode 100644
index 0000000000..dc2a874e10
--- /dev/null
+++ b/gemfiles/multi_json.gemfile
@@ -0,0 +1,36 @@
+# This file was generated by Appraisal
+
+source 'https://rubygems.org'
+
+gem 'multi_json', require: 'multi_json'
+
+group :development, :test do
+  gem 'bundler'
+  gem 'rake'
+  gem 'rubocop', '0.47.0'
+  gem 'hashie'
+end
+
+group :development do
+  gem 'guard'
+  gem 'guard-rspec'
+  gem 'guard-rubocop'
+  gem 'yard'
+  gem 'appraisal'
+  gem 'benchmark-ips'
+  gem 'redcarpet'
+end
+
+group :test do
+  gem 'grape-entity', '~> 0.6'
+  gem 'maruku'
+  gem 'rack-test'
+  gem 'rspec', '~> 3.0'
+  gem 'cookiejar'
+  gem 'rack-jsonp', require: 'rack/jsonp'
+  gem 'mime-types'
+  gem 'ruby-grape-danger', '~> 0.1.0', require: false
+  gem 'coveralls', '~> 0.8.17', require: false
+end
+
+gemspec path: '../'
diff --git a/gemfiles/multi_xml.gemfile b/gemfiles/multi_xml.gemfile
new file mode 100644
index 0000000000..af3b7eedfe
--- /dev/null
+++ b/gemfiles/multi_xml.gemfile
@@ -0,0 +1,36 @@
+# This file was generated by Appraisal
+
+source 'https://rubygems.org'
+
+gem 'multi_xml', require: 'multi_xml'
+
+group :development, :test do
+  gem 'bundler'
+  gem 'rake'
+  gem 'rubocop', '0.47.0'
+  gem 'hashie'
+end
+
+group :development do
+  gem 'guard'
+  gem 'guard-rspec'
+  gem 'guard-rubocop'
+  gem 'yard'
+  gem 'appraisal'
+  gem 'benchmark-ips'
+  gem 'redcarpet'
+end
+
+group :test do
+  gem 'grape-entity', '~> 0.6'
+  gem 'maruku'
+  gem 'rack-test'
+  gem 'rspec', '~> 3.0'
+  gem 'cookiejar'
+  gem 'rack-jsonp', require: 'rack/jsonp'
+  gem 'mime-types'
+  gem 'ruby-grape-danger', '~> 0.1.0', require: false
+  gem 'coveralls', '~> 0.8.17', require: false
+end
+
+gemspec path: '../'
diff --git a/grape.gemspec b/grape.gemspec
index 93e7777690..e2f43592a9 100644
--- a/grape.gemspec
+++ b/grape.gemspec
@@ -16,8 +16,6 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'mustermann-grape', '~> 1.0.0'
   s.add_runtime_dependency 'rack-accept'
   s.add_runtime_dependency 'activesupport'
-  s.add_runtime_dependency 'multi_json', '>= 1.3.2'
-  s.add_runtime_dependency 'multi_xml', '>= 0.5.2'
   s.add_runtime_dependency 'virtus', '>= 1.0.0'
   s.add_runtime_dependency 'builder'
 
diff --git a/lib/grape.rb b/lib/grape.rb
index 27a2e15280..d30ad3b530 100644
--- a/lib/grape.rb
+++ b/lib/grape.rb
@@ -16,8 +16,6 @@
 require 'active_support/core_ext/hash/conversions'
 require 'active_support/dependencies/autoload'
 require 'active_support/notifications'
-require 'multi_json'
-require 'multi_xml'
 require 'i18n'
 require 'thread'
 
@@ -44,6 +42,8 @@ module Grape
     autoload :Parser
     autoload :Request
     autoload :Env, 'grape/util/env'
+    autoload :Json, 'grape/util/json'
+    autoload :Xml, 'grape/util/xml'
   end
 
   module Http
diff --git a/lib/grape/error_formatter/json.rb b/lib/grape/error_formatter/json.rb
index 2885efd53d..e11210495c 100644
--- a/lib/grape/error_formatter/json.rb
+++ b/lib/grape/error_formatter/json.rb
@@ -10,7 +10,7 @@ def call(message, backtrace, options = {}, env = nil)
           if (options[:rescue_options] || {})[:backtrace] && backtrace && !backtrace.empty?
             result = result.merge(backtrace: backtrace)
           end
-          MultiJson.dump(result)
+          ::Grape::Json.dump(result)
         end
 
         private
diff --git a/lib/grape/error_formatter/txt.rb b/lib/grape/error_formatter/txt.rb
index 6813a5a98d..db8762f954 100644
--- a/lib/grape/error_formatter/txt.rb
+++ b/lib/grape/error_formatter/txt.rb
@@ -7,7 +7,7 @@ class << self
         def call(message, backtrace, options = {}, env = nil)
           message = present(message, env)
 
-          result = message.is_a?(Hash) ? MultiJson.dump(message) : message
+          result = message.is_a?(Hash) ? ::Grape::Json.dump(message) : message
           if (options[:rescue_options] || {})[:backtrace] && backtrace && !backtrace.empty?
             result += "\r\n "
             result += backtrace.join("\r\n ")
diff --git a/lib/grape/formatter/json.rb b/lib/grape/formatter/json.rb
index 353ee32e0c..5f96918b28 100644
--- a/lib/grape/formatter/json.rb
+++ b/lib/grape/formatter/json.rb
@@ -4,7 +4,7 @@ module Json
       class << self
         def call(object, _env)
           return object.to_json if object.respond_to?(:to_json)
-          MultiJson.dump(object)
+          ::Grape::Json.dump(object)
         end
       end
     end
diff --git a/lib/grape/formatter/serializable_hash.rb b/lib/grape/formatter/serializable_hash.rb
index 99cfb7b30e..c31fcebb0e 100644
--- a/lib/grape/formatter/serializable_hash.rb
+++ b/lib/grape/formatter/serializable_hash.rb
@@ -4,9 +4,9 @@ module SerializableHash
       class << self
         def call(object, _env)
           return object if object.is_a?(String)
-          return MultiJson.dump(serialize(object)) if serializable?(object)
+          return ::Grape::Json.dump(serialize(object)) if serializable?(object)
           return object.to_json if object.respond_to?(:to_json)
-          MultiJson.dump(object)
+          ::Grape::Json.dump(object)
         end
 
         private
diff --git a/lib/grape/parser/json.rb b/lib/grape/parser/json.rb
index 99c5ba0e94..89b50d3f2b 100644
--- a/lib/grape/parser/json.rb
+++ b/lib/grape/parser/json.rb
@@ -3,8 +3,8 @@ module Parser
     module Json
       class << self
         def call(object, _env)
-          MultiJson.load(object)
-        rescue MultiJson::ParseError
+          ::Grape::Json.load(object)
+        rescue ::Grape::Json::ParseError
           # handle JSON parsing errors via the rescue handlers or provide error message
           raise Grape::Exceptions::InvalidMessageBody, 'application/json'
         end
diff --git a/lib/grape/parser/xml.rb b/lib/grape/parser/xml.rb
index 5fa06f57e3..9fadf1c64f 100644
--- a/lib/grape/parser/xml.rb
+++ b/lib/grape/parser/xml.rb
@@ -3,8 +3,8 @@ module Parser
     module Xml
       class << self
         def call(object, _env)
-          MultiXml.parse(object)
-        rescue MultiXml::ParseError
+          ::Grape::Xml.parse(object)
+        rescue ::Grape::Xml::ParseError
           # handle XML parsing errors via the rescue handlers or provide error message
           raise Grape::Exceptions::InvalidMessageBody, 'application/xml'
         end
diff --git a/lib/grape/util/json.rb b/lib/grape/util/json.rb
new file mode 100644
index 0000000000..b0f5addb07
--- /dev/null
+++ b/lib/grape/util/json.rb
@@ -0,0 +1,8 @@
+module Grape
+  if Object.const_defined? :MultiJson
+    Json = ::MultiJson
+  else
+    Json = ::JSON
+    Json::ParseError = Json::ParserError
+  end
+end
diff --git a/lib/grape/util/xml.rb b/lib/grape/util/xml.rb
new file mode 100644
index 0000000000..dd5d296e6b
--- /dev/null
+++ b/lib/grape/util/xml.rb
@@ -0,0 +1,8 @@
+module Grape
+  if Object.const_defined? :MultiXml
+    Xml = ::MultiXml
+  else
+    Xml = ::ActiveSupport::XmlMini
+    Xml::ParseError = StandardError
+  end
+end
diff --git a/spec/grape/api/invalid_format_spec.rb b/spec/grape/api/invalid_format_spec.rb
index 1d7ad8336b..5747694484 100644
--- a/spec/grape/api/invalid_format_spec.rb
+++ b/spec/grape/api/invalid_format_spec.rb
@@ -27,17 +27,17 @@ def app
     it 'no format' do
       get '/foo'
       expect(last_response.status).to eq 200
-      expect(last_response.body).to eq(MultiJson.dump(id: 'foo', format: nil))
+      expect(last_response.body).to eq(::Grape::Json.dump(id: 'foo', format: nil))
     end
     it 'json format' do
       get '/foo.json'
       expect(last_response.status).to eq 200
-      expect(last_response.body).to eq(MultiJson.dump(id: 'foo', format: 'json'))
+      expect(last_response.body).to eq(::Grape::Json.dump(id: 'foo', format: 'json'))
     end
     it 'invalid format' do
       get '/foo.invalid'
       expect(last_response.status).to eq 200
-      expect(last_response.body).to eq(MultiJson.dump(id: 'foo', format: 'invalid'))
+      expect(last_response.body).to eq(::Grape::Json.dump(id: 'foo', format: 'invalid'))
     end
   end
 end
diff --git a/spec/grape/api_spec.rb b/spec/grape/api_spec.rb
index 8ed2ade68f..779893f8e2 100644
--- a/spec/grape/api_spec.rb
+++ b/spec/grape/api_spec.rb
@@ -1,6 +1,5 @@
 require 'spec_helper'
 require 'shared/versioning_examples'
-require 'grape-entity'
 
 describe Grape::API do
   subject { Class.new(Grape::API) }
@@ -444,9 +443,9 @@ class DummyFormatClass
             subject.send(verb) do
               env['api.request.body']
             end
-            send verb, '/', MultiJson.dump(object), 'CONTENT_TYPE' => 'application/json'
+            send verb, '/', ::Grape::Json.dump(object), 'CONTENT_TYPE' => 'application/json'
             expect(last_response.status).to eq(verb == :post ? 201 : 200)
-            expect(last_response.body).to eql MultiJson.dump(object)
+            expect(last_response.body).to eql ::Grape::Json.dump(object)
             expect(last_request.params).to eql({})
           end
           it 'stores input in api.request.input' do
@@ -454,9 +453,9 @@ class DummyFormatClass
             subject.send(verb) do
               env['api.request.input']
             end
-            send verb, '/', MultiJson.dump(object), 'CONTENT_TYPE' => 'application/json'
+            send verb, '/', ::Grape::Json.dump(object), 'CONTENT_TYPE' => 'application/json'
             expect(last_response.status).to eq(verb == :post ? 201 : 200)
-            expect(last_response.body).to eql MultiJson.dump(object).to_json
+            expect(last_response.body).to eql ::Grape::Json.dump(object).to_json
           end
           context 'chunked transfer encoding' do
             it 'stores input in api.request.input' do
@@ -464,9 +463,9 @@ class DummyFormatClass
               subject.send(verb) do
                 env['api.request.input']
               end
-              send verb, '/', MultiJson.dump(object), 'CONTENT_TYPE' => 'application/json', 'HTTP_TRANSFER_ENCODING' => 'chunked', 'CONTENT_LENGTH' => nil
+              send verb, '/', ::Grape::Json.dump(object), 'CONTENT_TYPE' => 'application/json', 'HTTP_TRANSFER_ENCODING' => 'chunked', 'CONTENT_LENGTH' => nil
               expect(last_response.status).to eq(verb == :post ? 201 : 200)
-              expect(last_response.body).to eql MultiJson.dump(object).to_json
+              expect(last_response.body).to eql ::Grape::Json.dump(object).to_json
             end
           end
         end
@@ -2053,7 +2052,7 @@ def self.call(message, _backtrace, _option, _env)
         raise 'rain!'
       end
       get '/exception'
-      json = MultiJson.load(last_response.body)
+      json = ::Grape::Json.load(last_response.body)
       expect(json['error']).to eql 'rain!'
       expect(json['backtrace'].length).to be > 0
     end
@@ -2225,14 +2224,27 @@ def self.call(object, _env)
         expect(last_response.body).to eql 'elpmis'
       end
     end
-    context 'multi_xml' do
-      it "doesn't parse yaml" do
-        subject.put :yaml do
-          params[:tag]
+    if Object.const_defined? :MultiXml
+      context 'multi_xml' do
+        it "doesn't parse yaml" do
+          subject.put :yaml do
+            params[:tag]
+          end
+          put '/yaml', '<tag type="symbol">a123</tag>', 'CONTENT_TYPE' => 'application/xml'
+          expect(last_response.status).to eq(400)
+          expect(last_response.body).to eql 'Disallowed type attribute: "symbol"'
+        end
+      end
+    else
+      context 'default xml parser' do
+        it 'parses symbols' do
+          subject.put :yaml do
+            params[:tag]
+          end
+          put '/yaml', '<tag type="symbol">a123</tag>', 'CONTENT_TYPE' => 'application/xml'
+          expect(last_response.status).to eq(200)
+          expect(last_response.body).to eql '{"type"=>"symbol", "__content__"=>"a123"}'
         end
-        put '/yaml', '<tag type="symbol">a123</tag>', 'CONTENT_TYPE' => 'application/xml'
-        expect(last_response.status).to eq(400)
-        expect(last_response.body).to eql 'Disallowed type attribute: "symbol"'
       end
     end
     context 'none parser class' do
@@ -3156,7 +3168,7 @@ def static
     end
     it 'path' do
       get '/endpoint/options'
-      options = MultiJson.load(last_response.body)
+      options = ::Grape::Json.load(last_response.body)
       expect(options['path']).to eq(['/endpoint/options'])
       expect(options['source_location'][0]).to include 'api_spec.rb'
       expect(options['source_location'][1].to_i).to be > 0
diff --git a/spec/grape/endpoint_spec.rb b/spec/grape/endpoint_spec.rb
index 8d678b6a9f..ff06105388 100644
--- a/spec/grape/endpoint_spec.rb
+++ b/spec/grape/endpoint_spec.rb
@@ -470,7 +470,7 @@ def app
         ''
       end
 
-      post '/declared', MultiJson.dump(first: 'one', boolean: false), 'CONTENT_TYPE' => 'application/json'
+      post '/declared', ::Grape::Json.dump(first: 'one', boolean: false), 'CONTENT_TYPE' => 'application/json'
       expect(last_response.status).to eq(201)
     end
 
@@ -485,7 +485,7 @@ def app
         ''
       end
 
-      post '/declared', MultiJson.dump(first: 'one', second: nil), 'CONTENT_TYPE' => 'application/json'
+      post '/declared', ::Grape::Json.dump(first: 'one', second: nil), 'CONTENT_TYPE' => 'application/json'
       expect(last_response.status).to eq(201)
     end
 
@@ -873,7 +873,7 @@ def app
       end
 
       it 'converts JSON bodies to params' do
-        post '/request_body', MultiJson.dump(user: 'Bobby T.'), 'CONTENT_TYPE' => 'application/json'
+        post '/request_body', ::Grape::Json.dump(user: 'Bobby T.'), 'CONTENT_TYPE' => 'application/json'
         expect(last_response.body).to eq('Bobby T.')
       end
 
@@ -882,14 +882,26 @@ def app
         expect(last_response.body).to eq('')
       end
 
-      it 'converts XML bodies to params' do
-        post '/request_body', '<user>Bobby T.</user>', 'CONTENT_TYPE' => 'application/xml'
-        expect(last_response.body).to eq('Bobby T.')
-      end
+      if Object.const_defined? :MultiXml
+        it 'converts XML bodies to params' do
+          post '/request_body', '<user>Bobby T.</user>', 'CONTENT_TYPE' => 'application/xml'
+          expect(last_response.body).to eq('Bobby T.')
+        end
 
-      it 'converts XML bodies to params' do
-        put '/request_body', '<user>Bobby T.</user>', 'CONTENT_TYPE' => 'application/xml'
-        expect(last_response.body).to eq('Bobby T.')
+        it 'converts XML bodies to params' do
+          put '/request_body', '<user>Bobby T.</user>', 'CONTENT_TYPE' => 'application/xml'
+          expect(last_response.body).to eq('Bobby T.')
+        end
+      else
+        it 'converts XML bodies to params' do
+          post '/request_body', '<user>Bobby T.</user>', 'CONTENT_TYPE' => 'application/xml'
+          expect(last_response.body).to eq('{"__content__"=>"Bobby T."}')
+        end
+
+        it 'converts XML bodies to params' do
+          put '/request_body', '<user>Bobby T.</user>', 'CONTENT_TYPE' => 'application/xml'
+          expect(last_response.body).to eq('{"__content__"=>"Bobby T."}')
+        end
       end
 
       it 'does not include parameters not defined by the body' do
@@ -897,7 +909,7 @@ def app
           error! 400, 'expected nil' if params[:version]
           params[:user]
         end
-        post '/omitted_params', MultiJson.dump(user: 'Bob'), 'CONTENT_TYPE' => 'application/json'
+        post '/omitted_params', ::Grape::Json.dump(user: 'Bob'), 'CONTENT_TYPE' => 'application/json'
         expect(last_response.status).to eq(201)
         expect(last_response.body).to eq('Bob')
       end
@@ -920,7 +932,7 @@ def app
       subject.put '/request_body' do
         params[:user]
       end
-      put '/request_body', MultiJson.dump(user: 'Bob'), 'CONTENT_TYPE' => 'text/plain'
+      put '/request_body', ::Grape::Json.dump(user: 'Bob'), 'CONTENT_TYPE' => 'text/plain'
 
       expect(last_response.status).to eq(406)
       expect(last_response.body).to eq('{"error":"The requested content-type \'text/plain\' is not supported."}')
@@ -934,7 +946,7 @@ def app
         subject.post do
           params[:data]
         end
-        post '/', MultiJson.dump(data: { some: 'payload' }), 'CONTENT_TYPE' => 'application/json'
+        post '/', ::Grape::Json.dump(data: { some: 'payload' }), 'CONTENT_TYPE' => 'application/json'
       end
 
       it 'should not response with 406 for same type without params' do
diff --git a/spec/grape/middleware/formatter_spec.rb b/spec/grape/middleware/formatter_spec.rb
index a094f5bf6a..c90f6c1f9b 100644
--- a/spec/grape/middleware/formatter_spec.rb
+++ b/spec/grape/middleware/formatter_spec.rb
@@ -11,7 +11,7 @@
     let(:body) { { 'abc' => 'def' } }
     it 'looks at the bodies for possibly serializable data' do
       _, _, bodies = *subject.call('PATH_INFO' => '/somewhere', 'HTTP_ACCEPT' => 'application/json')
-      bodies.each { |b| expect(b).to eq(MultiJson.dump(body)) }
+      bodies.each { |b| expect(b).to eq(::Grape::Json.dump(body)) }
     end
 
     context 'default format' do
@@ -274,7 +274,11 @@ def to_xml
           'rack.input' => io,
           'CONTENT_LENGTH' => io.length
         )
-        expect(subject.env['rack.request.form_hash']['thing']['name']).to eq('Test')
+        if Object.const_defined? :MultiXml
+          expect(subject.env['rack.request.form_hash']['thing']['name']).to eq('Test')
+        else
+          expect(subject.env['rack.request.form_hash']['thing']['name']['__content__']).to eq('Test')
+        end
       end
       [Rack::Request::FORM_DATA_MEDIA_TYPES, Rack::Request::PARSEABLE_DATA_MEDIA_TYPES].flatten.each do |content_type|
         it "ignores #{content_type}" do
diff --git a/spec/integration/multi_json/json_spec.rb b/spec/integration/multi_json/json_spec.rb
new file mode 100644
index 0000000000..11ae851322
--- /dev/null
+++ b/spec/integration/multi_json/json_spec.rb
@@ -0,0 +1,7 @@
+require 'spec_helper'
+
+describe Grape::Json do
+  it 'uses multi_json' do
+    expect(Grape::Json).to eq(::MultiJson)
+  end
+end
diff --git a/spec/integration/multi_xml/xml_spec.rb b/spec/integration/multi_xml/xml_spec.rb
new file mode 100644
index 0000000000..fce3c51ed8
--- /dev/null
+++ b/spec/integration/multi_xml/xml_spec.rb
@@ -0,0 +1,7 @@
+require 'spec_helper'
+
+describe Grape::Xml do
+  it 'uses multi_xml' do
+    expect(Grape::Xml).to eq(::MultiXml)
+  end
+end