diff --git a/actionpack/lib/action_controller/testing/integration.rb b/actionpack/lib/action_controller/testing/integration.rb
index be5f216e2b..037463e489 100644
--- a/actionpack/lib/action_controller/testing/integration.rb
+++ b/actionpack/lib/action_controller/testing/integration.rb
@@ -263,7 +263,6 @@ module ActionController
           opts = {
             :method => method.to_s.upcase,
             :params => parameters,
-            :headers => headers,
 
             "SERVER_NAME"     => host,
             "SERVER_PORT"     => (https? ? "443" : "80"),
@@ -282,6 +281,12 @@ module ActionController
           }
           env = ActionDispatch::Test::MockRequest.env_for(@path, opts)
 
+          (headers || {}).each do |key, value|
+            key = key.to_s.upcase.gsub(/-/, "_")
+            key = "HTTP_#{key}" unless env.has_key?(key) || key =~ /^HTTP_/
+            env[key] = value
+          end
+
           app = Rack::Lint.new(@app)
           status, headers, body = app.call(env)
           response = ::Rack::MockResponse.new(status, headers, body)
diff --git a/actionpack/lib/action_dispatch/test/mock.rb b/actionpack/lib/action_dispatch/test/mock.rb
index 8dc048af11..4042f9fbc8 100644
--- a/actionpack/lib/action_dispatch/test/mock.rb
+++ b/actionpack/lib/action_dispatch/test/mock.rb
@@ -5,8 +5,6 @@ module ActionDispatch
 
       class << self
         def env_for(path, opts)
-          headers = opts.delete(:headers)
-
           method = (opts[:method] || opts["REQUEST_METHOD"]).to_s.upcase
           opts[:method] = opts["REQUEST_METHOD"] = method
 
@@ -48,15 +46,7 @@ module ActionDispatch
             uri.query = requestify(params)
           end
 
-          env = ::Rack::MockRequest.env_for(uri.to_s, opts)
-
-          (headers || {}).each do |key, value|
-            key = key.to_s.upcase.gsub(/-/, "_")
-            key = "HTTP_#{key}" unless env.has_key?(key) || key =~ /^HTTP_/
-            env[key] = value
-          end
-
-          env
+          ::Rack::MockRequest.env_for(uri.to_s, opts)
         end
 
         private