diff --git a/.travis.yml b/.travis.yml
index d86d51f..86a4d33 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,3 +5,6 @@ rvm:
   - jruby
   - rbx
   - ree
+gemfiles:
+  - Gemfile
+  - Gemfile.rack-1.3.x
\ No newline at end of file
diff --git a/Gemfile b/Gemfile
index fa75df1..586864f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,4 @@
 source 'https://rubygems.org'
 
+gem 'rack', '~> 1.4'
 gemspec
diff --git a/Gemfile.rack-1.3.x b/Gemfile.rack-1.3.x
new file mode 100644
index 0000000..8ca314f
--- /dev/null
+++ b/Gemfile.rack-1.3.x
@@ -0,0 +1,4 @@
+source 'https://rubygems.org'
+
+gem 'rack', '~> 1.3.0'
+gemspec
\ No newline at end of file
diff --git a/lib/omniauth/builder.rb b/lib/omniauth/builder.rb
index bcb16b7..363e4ad 100644
--- a/lib/omniauth/builder.rb
+++ b/lib/omniauth/builder.rb
@@ -2,6 +2,19 @@ require 'omniauth'
 
 module OmniAuth
   class Builder < ::Rack::Builder
+    def initialize(app, &block)
+      if rack14?
+        super
+      else
+        @app = app
+        super(&block)
+      end
+    end
+
+    def rack14?
+      Rack.release.split('.')[1].to_i >= 4
+    end
+
     def on_failure(&block)
       OmniAuth.config.on_failure = block
     end
@@ -25,6 +38,7 @@ module OmniAuth
     end
 
     def call(env)
+      @ins << @app unless rack14? || @ins.include?(@app)
       to_app.call(env)
     end
   end
diff --git a/omniauth.gemspec b/omniauth.gemspec
index a016f9d..a8f96b3 100644
--- a/omniauth.gemspec
+++ b/omniauth.gemspec
@@ -7,7 +7,7 @@ Gem::Specification.new do |gem|
   gem.authors = ['Michael Bleigh', 'Erik Michaels-Ober']
   gem.email = ['michael@intridea.com', 'sferik@gmail.com']
 
-  gem.add_runtime_dependency 'rack', '~> 1.4'
+  gem.add_runtime_dependency 'rack'
   gem.add_runtime_dependency 'hashie', '~> 1.2'
 
   gem.add_development_dependency 'growl'
@@ -19,7 +19,7 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency 'rake'
   gem.add_development_dependency 'rb-fsevent'
   gem.add_development_dependency 'rdiscount'
-  gem.add_development_dependency 'rspec'
+  gem.add_development_dependency 'rspec', '~> 2.8'
   gem.add_development_dependency 'yard'
 
   gem.version = OmniAuth::VERSION