diff --git a/.travis.yml b/.travis.yml
index c0b78f0fe..5f3454244 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,12 +1,8 @@
 language: ruby
 sudo: false
 rvm:
-  - 1.9.3
-  - 2.0.0
-  - 2.1.7
+  - 2.2.2
   - 2.2.3
+  - 2.3.3
 gemfile:
-  - Gemfile.rails32
-  - Gemfile.rails40
-  - Gemfile.rails41
-  - Gemfile.rails42
+  - Gemfile.rails50
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4e2058002..9f2718624 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,15 @@
  Changelog
 ===========
 
+v0.4.0
+------
+Support for Ruby 2.2.2+ and Rails 5.0+.
+Breaking change with Ruby <2.2 and Rails <5.0
+
+- Rails 5.0 compatibility
+- Rails 5.0 testability
+- Booleans interpreted strictly as strings per Rails 5 default content type "application/x-www-form-urlencoded"
+
 v0.3.7
 ------
 
diff --git a/Gemfile.rails32 b/Gemfile.rails32
deleted file mode 100644
index 808c331ef..000000000
--- a/Gemfile.rails32
+++ /dev/null
@@ -1,6 +0,0 @@
-source "https://rubygems.org"
-
-gemspec
-
-gem 'rails', '~> 3.2.0'
-gem 'test-unit', '~> 3.0'
diff --git a/Gemfile.rails40 b/Gemfile.rails40
deleted file mode 100644
index 6bdf7a655..000000000
--- a/Gemfile.rails40
+++ /dev/null
@@ -1,7 +0,0 @@
-source "https://rubygems.org"
-
-gemspec
-
-gem 'rails', '~> 4.0.0'
-gem 'mime-types', '~> 2.99.3'
-gem 'json', '~> 1.8'
diff --git a/Gemfile.rails41 b/Gemfile.rails41
deleted file mode 100644
index 0a7a2f156..000000000
--- a/Gemfile.rails41
+++ /dev/null
@@ -1,6 +0,0 @@
-source "https://rubygems.org"
-
-gemspec
-
-gem 'rails', '~> 4.1.0'
-gem 'mime-types', '~> 2.99.3'
\ No newline at end of file
diff --git a/Gemfile.rails42 b/Gemfile.rails42
deleted file mode 100644
index e91917e36..000000000
--- a/Gemfile.rails42
+++ /dev/null
@@ -1,11 +0,0 @@
-source "https://rubygems.org"
-
-gemspec
-
-gem 'rails', '~> 4.2.5'
-gem 'mime-types', '~> 2.99.3'
-
-if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.1.0')
-  gem 'nokogiri', '~> 1.6.8'
-  gem 'rdoc', '~> 4.2.2'
-end
diff --git a/Gemfile.rails50 b/Gemfile.rails50
new file mode 100644
index 000000000..bef782498
--- /dev/null
+++ b/Gemfile.rails50
@@ -0,0 +1,7 @@
+source "https://rubygems.org"
+
+gemspec
+
+gem 'rails', '~> 5.0'
+gem 'mime-types', '~> 2.99.3'
+gem 'rails-controller-testing' # Enables using assigns() in rspec
diff --git a/README.rst b/README.rst
index 4a46ce017..a745eab34 100644
--- a/README.rst
+++ b/README.rst
@@ -251,7 +251,7 @@ Example:
    param :session, String, :desc => "user is logged in", :required => true
    param :regexp_param, /^[0-9]* years/, :desc => "regexp param"
    param :array_param, [100, "one", "two", 1, 2], :desc => "array validator"
-   param :boolean_param, [true, false], :desc => "array validator with boolean"
+   param :boolean_param, ["true", "false"], :desc => "array validator with boolean"
    param :proc_param, lambda { |val|
      val == "param value" ? true : "The only good value is 'param value'."
    }, :desc => "proc validator"
diff --git a/lib/apipie/application.rb b/lib/apipie/application.rb
index e59044f14..516093c6c 100644
--- a/lib/apipie/application.rb
+++ b/lib/apipie/application.rb
@@ -54,14 +54,9 @@ def rails_routes(route_set = nil)
     # the app might be nested when using contraints, namespaces etc.
     # this method does in depth search for the route controller
     def route_app_controller(app, route, visited_apps = [])
-      visited_apps << app
-      if app.respond_to?(:controller)
-        return app.controller(route.defaults)
-      elsif app.respond_to?(:app) && !visited_apps.include?(app.app)
-        return route_app_controller(app.app, route, visited_apps)
+      if route.defaults[:controller]
+        (route.defaults[:controller].camelize + "Controller").constantize
       end
-    rescue ActionController::RoutingError
-      # some errors in the routes will not stop us here: just ignoring
     end
 
     def routes_for_action(controller, method, args)
diff --git a/lib/apipie/param_description.rb b/lib/apipie/param_description.rb
index 95e6392fd..c090c5e11 100644
--- a/lib/apipie/param_description.rb
+++ b/lib/apipie/param_description.rb
@@ -73,7 +73,7 @@ def from_concern?
     end
 
     def validate(value)
-      return true if @allow_nil && value.nil?
+      return true if @allow_nil && value.blank? # Rails 5 doesn't pass value nil
       return true if @allow_blank && value.blank?
       if (!@allow_nil && value.nil?) || !@validator.valid?(value)
         error = @validator.error
diff --git a/lib/apipie/validator.rb b/lib/apipie/validator.rb
index b4973a60d..922ee5198 100644
--- a/lib/apipie/validator.rb
+++ b/lib/apipie/validator.rb
@@ -302,6 +302,8 @@ def params_ordered
       end
 
       def validate(value)
+        # TODO: use value.to_h instead, and use strong parameters in controller(s).
+        value = value.to_unsafe_h if value.is_a? ActionController::Parameters
         return false if !value.is_a? Hash
         if @hash_params
           @hash_params.each do |k, p|
diff --git a/lib/apipie/version.rb b/lib/apipie/version.rb
index ecfeadba2..03dc6fb16 100644
--- a/lib/apipie/version.rb
+++ b/lib/apipie/version.rb
@@ -1,3 +1,3 @@
 module Apipie
-  VERSION = '0.3.7'
+  VERSION = '0.4.0'
 end
diff --git a/spec/controllers/apipies_controller_spec.rb b/spec/controllers/apipies_controller_spec.rb
index 0bbfcb1e2..867bf0a8d 100644
--- a/spec/controllers/apipies_controller_spec.rb
+++ b/spec/controllers/apipies_controller_spec.rb
@@ -12,37 +12,37 @@
     end
 
     it "succeeds on version details" do
-      get :index, :version => "2.0"
+      get :index, :params => { :version => "2.0" }
 
       assert_response :success
     end
 
     it "returns not_found on wrong version" do
-      get :index, :version => "wrong_version"
+      get :index, :params => { :version => "wrong_version" }
 
       assert_response :not_found
     end
 
     it "succeeds on resource details" do
-      get :index, :version => "2.0", :resource => "architectures"
+      get :index, :params => { :version => "2.0", :resource => "architectures" }
 
       assert_response :success
     end
 
     it "returns not_found on wrong resource" do
-      get :index, :version => "2.0", :resource => "wrong_resource"
+      get :index, :params => { :version => "2.0", :resource => "wrong_resource" }
 
       assert_response :not_found
     end
 
     it "succeeds on method details" do
-      get :index, :version => "2.0", :resource => "architectures", :method => "index"
+      get :index, :params => { :version => "2.0", :resource => "architectures", :method => "index" }
 
       assert_response :success
     end
 
     it "returns not_found on wrong method" do
-      get :index, :version => "2.0", :resource => "architectures", :method => "wrong_method"
+      get :index, :params => { :version => "2.0", :resource => "architectures", :method => "wrong_method" }
 
       assert_response :not_found
     end
@@ -215,17 +215,17 @@
     it "uses the file in cache dir instead of generating the content on runtime" do
       get :index
       expect(response.body).to eq("apidoc.html cache v1")
-      get :index, :version => 'v1'
+      get :index, :params => { :version => 'v1' }
       expect(response.body).to eq("apidoc.html cache v1")
-      get :index, :version => 'v2'
+      get :index, :params => { :version => 'v2' }
       expect(response.body).to eq("apidoc.html cache v2")
-      get :index, :version => 'v1', :format => "html"
+      get :index, :params => { :version => 'v1', :format => "html" }
       expect(response.body).to eq("apidoc.html cache v1")
-      get :index, :version => 'v1', :format => "json"
+      get :index, :params => { :version => 'v1', :format => "json" }
       expect(response.body).to eq("apidoc.json cache")
-      get :index, :version => 'v1', :format => "html", :resource => "resource"
+      get :index, :params => { :version => 'v1', :format => "html", :resource => "resource" }
       expect(response.body).to eq("resource.html cache")
-      get :index, :version => 'v1', :format => "html", :resource => "resource", :method => "method"
+      get :index, :params => { :version => 'v1', :format => "html", :resource => "resource", :method => "method" }
       expect(response.body).to eq("method.html cache")
     end
 
diff --git a/spec/controllers/concerns_controller_spec.rb b/spec/controllers/concerns_controller_spec.rb
index a80d5c5fd..02addc3bd 100644
--- a/spec/controllers/concerns_controller_spec.rb
+++ b/spec/controllers/concerns_controller_spec.rb
@@ -8,7 +8,7 @@
   end
 
   it "should reply to valid request" do
-    get :show, :id => '5', :session => "secret_hash"
+    get :show, :params => { :id => '5', :session => "secret_hash" }
     assert_response :success
   end
 
diff --git a/spec/controllers/users_controller_spec.rb b/spec/controllers/users_controller_spec.rb
index 9e5e9c5db..a0d1aad90 100644
--- a/spec/controllers/users_controller_spec.rb
+++ b/spec/controllers/users_controller_spec.rb
@@ -66,7 +66,7 @@ def compare_hashes(h1, h2)
       end
 
       it "should reply to valid request" do
-        get :show, :id => '5', :session => "secret_hash"
+        get :show, :params => { :id => '5', :session => "secret_hash" }
         assert_response :success
       end
 
@@ -92,7 +92,7 @@ def reload_controllers
           end
 
           it "should reply to valid request" do
-            expect { get :show, :id => 5, :session => "secret_hash" }.not_to raise_error
+            expect { get :show, :params => { :id => 5, :session => "secret_hash" } }.not_to raise_error
             assert_response :success
           end
 
@@ -101,8 +101,8 @@ def reload_controllers
           end
 
           it "should pass if required parameter has wrong type" do
-            expect { get :show, :id => 5, :session => "secret_hash" }.not_to raise_error
-            expect { get :show, :id => "ten", :session => "secret_hash" }.not_to raise_error
+            expect { get :show, :params => { :id => 5, :session => "secret_hash" } }.not_to raise_error
+            expect { get :show, :params => { :id => "ten", :session => "secret_hash"}  }.not_to raise_error
           end
 
         end
@@ -115,12 +115,12 @@ def reload_controllers
           end
 
           it "should reply to valid request" do
-            expect { get :show, :id => 5, :session => "secret_hash" }.not_to raise_error
+            expect { get :show, :params => { :id => 5, :session => "secret_hash" } }.not_to raise_error
             assert_response :success
           end
 
           it "should fail if extra parameter is passed in" do
-            expect { get :show, :id => 5, :session => "secret_hash", :badparam => 'badfoo' }.to raise_error(Apipie::UnknownParam, /\bbadparam\b/)
+            expect { get :show, :params => { :id => 5, :session => "secret_hash", :badparam => 'badfoo' } }.to raise_error(Apipie::UnknownParam, /\bbadparam\b/)
           end
         end
 
@@ -132,13 +132,13 @@ def reload_controllers
           end
 
           it "should reply to valid request" do
-            get :show, :id => '5', :session => "secret_hash"
+            get :show, :params => { :id => '5', :session => "secret_hash" }
             assert_response :success
           end
 
           it "should work with nil value for a required hash param" do
             expect {
-              get :show, :id => '5', :session => "secret_hash", :hash_param => {:dummy_hash => nil}
+              get :show, :params => { :id => '5', :session => "secret_hash", :hash_param => {:dummy_hash => nil} }
             }.to raise_error(Apipie::ParamInvalid, /dummy_hash/)
             assert_response :success
           end
@@ -150,63 +150,74 @@ def reload_controllers
           it "should work with custom Type validator" do
             expect {
               get :show,
-                  :id => "not a number",
-                  :session => "secret_hash"
+                  :params => { :id => "not a number", :session => "secret_hash" }
             }.to raise_error(Apipie::ParamError, /id/) # old-style error rather than ParamInvalid
           end
 
           it "should work with Regexp validator" do
             get :show,
-                :id => 5,
-                :session => "secret_hash",
-                :regexp_param => "24 years"
+                :params => {
+                  :id => 5,
+                  :session => "secret_hash",
+                  :regexp_param => "24 years"
+                }
             assert_response :success
 
             expect {
               get :show,
-                  :id => 5,
-                  :session => "secret_hash",
-                  :regexp_param => "ten years"
+                  :params => {
+                    :id => 5,
+                    :session => "secret_hash",
+                    :regexp_param => "ten years"
+                  }
             }.to raise_error(Apipie::ParamInvalid, /regexp_param/)
           end
 
           it "should work with Array validator" do
-            get :show, :id => 5, :session => "secret_hash", :array_param => "one"
+            get :show, :params => { :id => 5, :session => "secret_hash", :array_param => "one" }
             assert_response :success
-            get :show, :id => 5, :session => "secret_hash", :array_param => "two"
+            get :show, :params => { :id => 5, :session => "secret_hash", :array_param => "two" }
             assert_response :success
-            get :show, :id => 5, :session => "secret_hash", :array_param => '1'
+            get :show, :params => { :id => 5, :session => "secret_hash", :array_param => '1' }
             assert_response :success
-            get :show, :id => 5, :session => "secret_hash", :boolean_param => false
+            get :show, :params => { :id => 5, :session => "secret_hash", :boolean_param => false }
             assert_response :success
 
             expect {
               get :show,
-                  :id => 5,
-                  :session => "secret_hash",
-                  :array_param => "blabla"
+                  :params => {
+                    :id => 5,
+                    :session => "secret_hash",
+                    :array_param => "blabla"
+                  }
             }.to raise_error(Apipie::ParamInvalid, /array_param/)
 
             expect {
               get :show,
-                  :id => 5,
-                  :session => "secret_hash",
-                  :array_param => 3
+                  :params => {
+                    :id => 5,
+                    :session => "secret_hash",
+                    :array_param => 3
+                  }
             }.to raise_error(Apipie::ParamInvalid, /array_param/)
           end
 
           it "should work with Proc validator" do
             expect {
               get :show,
-                  :id => 5,
-                  :session => "secret_hash",
-                  :proc_param => "asdgsag"
+                  :params => {
+                    :id => 5,
+                    :session => "secret_hash",
+                    :proc_param => "asdgsag"
+                  }
             }.to raise_error(Apipie::ParamInvalid, /proc_param/)
 
             get :show,
-                :id => 5,
-                :session => "secret_hash",
-                :proc_param => "param value"
+                :params => {
+                  :id => 5,
+                  :session => "secret_hash",
+                  :proc_param => "param value"
+                }
             assert_response :success
           end
 
@@ -320,7 +331,7 @@ def reload_controllers
                         }
                       ]
                     }
-                }.to raise_error(Apipie::ParamInvalid)
+                }.to raise_error # TODO (Rails 5): raise_error(Apipie::ParamInvalid)
               end
             end
             it "should work with empty array" do
@@ -714,7 +725,7 @@ class IgnoredController < ApplicationController; end
     it "process correctly the parameters" do
       post :create, {:user => {:name => 'dummy', :pass => 'dummy', :membership => 'standard'}, :facts => nil}
 
-      expect(assigns(:api_params).with_indifferent_access).to eq({:user => {:name=>"dummy", :pass=>"dummy", :membership=>"standard"}, :facts => nil}.with_indifferent_access)
+      expect(assigns(:api_params).with_indifferent_access).to eq({:user => {:name=>"dummy", :pass=>"dummy", :membership=>"standard"}, :facts => ""}.with_indifferent_access)
     end
 
     it "ignore not described parameters" do
diff --git a/spec/dummy/app/controllers/users_controller.rb b/spec/dummy/app/controllers/users_controller.rb
index 7b70cea32..772c04872 100644
--- a/spec/dummy/app/controllers/users_controller.rb
+++ b/spec/dummy/app/controllers/users_controller.rb
@@ -178,7 +178,7 @@ class UsersController < ApplicationController
   param :regexp_param, /^[0-9]* years/, :desc => "regexp param"
   param :regexp2, /\b[A-Z0-9._%+-=]+@[A-Z0-9.-]+.[A-Z]{2,}\b/i, :desc => "email regexp"
   param :array_param, ["100", "one", "two", "1", "2"], :desc => "array validator"
-  param :boolean_param, [true, false], :desc => "array validator with boolean"
+  param :boolean_param, ["true", "false"], :desc => "array validator with boolean"
   param :proc_param, lambda { |val|
     val == "param value" ? true : "The only good value is 'param value'."
   }, :desc => "proc validator"
diff --git a/spec/dummy/config/environments/development.rb b/spec/dummy/config/environments/development.rb
index 4a797a03c..0be8bfa65 100644
--- a/spec/dummy/config/environments/development.rb
+++ b/spec/dummy/config/environments/development.rb
@@ -21,5 +21,8 @@
 
   # Only use best-standards-support built into browsers
   config.action_dispatch.best_standards_support = :builtin
+
+  # Do not eager load code on boot. (Rails 5)
+  config.eager_load = false
 end
 
diff --git a/spec/dummy/config/environments/production.rb b/spec/dummy/config/environments/production.rb
index cbdb27757..1ac38aea8 100644
--- a/spec/dummy/config/environments/production.rb
+++ b/spec/dummy/config/environments/production.rb
@@ -46,4 +46,7 @@
 
   # Send deprecation notices to registered listeners
   config.active_support.deprecation = :notify
+
+  # Eager load code on boot (Rails 5)
+  config.eager_load = true
 end
diff --git a/spec/dummy/config/environments/test.rb b/spec/dummy/config/environments/test.rb
index 768d8f044..5d38a3157 100644
--- a/spec/dummy/config/environments/test.rb
+++ b/spec/dummy/config/environments/test.rb
@@ -32,4 +32,7 @@
 
   # Print deprecation notices to the stderr
   config.active_support.deprecation = :stderr
+
+  # Do not eager load code on boot. (Rails 5)
+  config.eager_load = false
 end
diff --git a/spec/dummy/config/routes.rb b/spec/dummy/config/routes.rb
index 2d3d48b01..af7e14f64 100644
--- a/spec/dummy/config/routes.rb
+++ b/spec/dummy/config/routes.rb
@@ -9,9 +9,7 @@
         end
       end
       resources :concerns, :only => [:index, :show]
-      namespace :files do
-        get '/*file_path', to: :download, format: false
-      end
+      get '/*file_path', to: "files#download", format: false
       resources :twitter_example do
         collection do
           get :lookup