diff --git a/.travis.yml b/.travis.yml
index 2dd7a06..f674235 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,3 +15,4 @@ notifications:
 gemfile:
   - Gemfile
   - gemfiles/mongoid3.gemfile
+  - gemfiles/mongoid4.gemfile
diff --git a/Gemfile b/Gemfile
index cf9030f..a24d5a6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,7 +3,5 @@ source 'https://rubygems.org'
 # Specify your gem's dependencies in searchkick.gemspec
 gemspec
 
-# gem "mongoid", github: "mongoid/mongoid"
-# gem "mongoid", "~> 3.1.0"
 # gem "activerecord", "~> 3.2.0"
 # gem "activerecord", "~> 3.1.0"
diff --git a/gemfiles/mongoid4.gemfile b/gemfiles/mongoid4.gemfile
new file mode 100644
index 0000000..f72ac6d
--- /dev/null
+++ b/gemfiles/mongoid4.gemfile
@@ -0,0 +1,6 @@
+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in searchkick.gemspec
+gemspec path: "../"
+
+gem "mongoid", github: "mongoid/mongoid"
diff --git a/lib/searchkick/model.rb b/lib/searchkick/model.rb
index 035c357..933512f 100644
--- a/lib/searchkick/model.rb
+++ b/lib/searchkick/model.rb
@@ -43,6 +43,9 @@ module Searchkick
           # stringify fields
           source = source.inject({}){|memo,(k,v)| memo[k.to_s] = v; memo}
 
+          # Mongoid 4 hack
+          source["_id"] = source["_id"].to_s if source["_id"]
+
           options = self.class.searchkick_options
 
           # conversions
diff --git a/searchkick.gemspec b/searchkick.gemspec
index 97cd837..0e60113 100644
--- a/searchkick.gemspec
+++ b/searchkick.gemspec
@@ -23,7 +23,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "bundler", "~> 1.3"
   spec.add_development_dependency "rake"
-  spec.add_development_dependency "minitest"
+  spec.add_development_dependency "minitest", "~> 4.7"
   spec.add_development_dependency "activerecord"
   spec.add_development_dependency "pg"
 end
diff --git a/test/autocomplete_test.rb b/test/autocomplete_test.rb
index dd2f3a6..7bc76dd 100644
--- a/test/autocomplete_test.rb
+++ b/test/autocomplete_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestAutocomplete < Minitest::Test
+class TestAutocomplete < Minitest::Unit::TestCase
 
   def test_autocomplete
     store_names ["Hummus"]
diff --git a/test/boost_test.rb b/test/boost_test.rb
index 94c038c..8e955b1 100644
--- a/test/boost_test.rb
+++ b/test/boost_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestBoost < Minitest::Test
+class TestBoost < Minitest::Unit::TestCase
 
   # conversions
 
diff --git a/test/facets_test.rb b/test/facets_test.rb
index 2bee171..22f9814 100644
--- a/test/facets_test.rb
+++ b/test/facets_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestFacets < Minitest::Test
+class TestFacets < Minitest::Unit::TestCase
 
   def setup
     super
diff --git a/test/highlight_test.rb b/test/highlight_test.rb
index f35034c..04ae2ad 100644
--- a/test/highlight_test.rb
+++ b/test/highlight_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestHighlight < Minitest::Test
+class TestHighlight < Minitest::Unit::TestCase
 
   def test_basic
     store_names ["Two Door Cinema Club"]
diff --git a/test/index_test.rb b/test/index_test.rb
index 6fcabf9..c4e7302 100644
--- a/test/index_test.rb
+++ b/test/index_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestIndex < Minitest::Test
+class TestIndex < Minitest::Unit::TestCase
 
   def test_clean_indices
     old_index = Tire::Index.new("products_test_20130801000000000")
diff --git a/test/inheritance_test.rb b/test/inheritance_test.rb
index b770de9..1c9022f 100644
--- a/test/inheritance_test.rb
+++ b/test/inheritance_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestInheritance < Minitest::Test
+class TestInheritance < Minitest::Unit::TestCase
 
   def setup
     super
diff --git a/test/match_test.rb b/test/match_test.rb
index 65d50ca..679100a 100644
--- a/test/match_test.rb
+++ b/test/match_test.rb
@@ -2,7 +2,7 @@
 
 require_relative "test_helper"
 
-class TestMatch < Minitest::Test
+class TestMatch < Minitest::Unit::TestCase
 
   # exact
 
diff --git a/test/similar_test.rb b/test/similar_test.rb
index 685d514..b36ceac 100644
--- a/test/similar_test.rb
+++ b/test/similar_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestSimilar < Minitest::Test
+class TestSimilar < Minitest::Unit::TestCase
 
   def test_similar
     store_names ["Annie's Naturals Organic Shiitake & Sesame Dressing"]
diff --git a/test/sql_test.rb b/test/sql_test.rb
index 47a3c3f..6a4fe95 100644
--- a/test/sql_test.rb
+++ b/test/sql_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestSql < Minitest::Test
+class TestSql < Minitest::Unit::TestCase
 
   def test_limit
     store_names ["Product A", "Product B", "Product C", "Product D"]
@@ -87,7 +87,7 @@ class TestSql < Minitest::Test
   def test_where_id
     store_names ["Product A"]
     product = Product.last
-    assert_search "product", ["Product A"], where: {id: product.id}
+    assert_search "product", ["Product A"], where: {id: product.id.to_s}
   end
 
   def test_near
diff --git a/test/suggest_test.rb b/test/suggest_test.rb
index f7d5251..250cf34 100644
--- a/test/suggest_test.rb
+++ b/test/suggest_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestSuggest < Minitest::Test
+class TestSuggest < Minitest::Unit::TestCase
 
   def test_basic
     store_names ["Great White Shark", "Hammerhead Shark", "Tiger Shark"]
diff --git a/test/synonyms_test.rb b/test/synonyms_test.rb
index aea3d26..3e02c20 100644
--- a/test/synonyms_test.rb
+++ b/test/synonyms_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-class TestSynonyms < Minitest::Test
+class TestSynonyms < Minitest::Unit::TestCase
 
   def test_bleach
     store_names ["Clorox Bleach", "Kroger Bleach"]
diff --git a/test/test_helper.rb b/test/test_helper.rb
index f6eda9d..7d8b3d5 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -18,8 +18,15 @@ if defined?(Mongoid)
 
   class Product
     include Mongoid::Document
-    # include Mongoid::Attributes::Dynamic
-
+    include Mongoid::Timestamps
+
+    field :name
+    field :store_id, type: Integer
+    field :in_stock, type: Boolean
+    field :backordered, type: Boolean
+    field :orders_count, type: Integer
+    field :price, type: Integer
+    field :color
     field :latitude, type: BigDecimal
     field :longitude, type: BigDecimal
   end
@@ -30,6 +37,8 @@ if defined?(Mongoid)
 
   class Animal
     include Mongoid::Document
+
+    field :name
   end
 
   class Dog < Animal
@@ -122,7 +131,7 @@ Product.reindex # run twice for both index paths
 
 Animal.reindex
 
-class Minitest::Test
+class Minitest::Unit::TestCase
 
   def setup
     Product.destroy_all
--
libgit2 0.21.0