2 files changed, 11 insertions, 8 deletions
diff --git a/actionpack/lib/action_controller/metal/live.rb b/actionpack/lib/action_controller/metal/live.rb
index bba75b22fd..32e5afa335 100644
--- a/actionpack/lib/action_controller/metal/live.rb
+++ b/actionpack/lib/action_controller/metal/live.rb
@@ -81,11 +81,6 @@ module ActionController
         end
       end
 
-      def initialize(status = 200, header = {}, body = [])
-        header = Header.new self, header
-        super(status, header, body)
-      end
-
       def commit!
         headers.freeze
         super
@@ -98,6 +93,10 @@ module ActionController
         body.each { |part| buf.write part }
         buf
       end
+
+      def merge_default_headers(original, default)
+        Header.new self, super
+      end
     end
 
     def process(name)
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index 5014ad80aa..11b7534ea4 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -97,9 +97,7 @@ module ActionDispatch # :nodoc:
     def initialize(status = 200, header = {}, body = [])
       super()
 
-      if self.class.default_headers.respond_to?(:merge)
-        header = self.class.default_headers.merge(header)
-      end
+      header = merge_default_headers(header, self.class.default_headers)
 
       self.body, self.header, self.status = body, header, status
 
@@ -243,6 +241,12 @@ module ActionDispatch # :nodoc:
 
   private
 
+    def merge_default_headers(original, default)
+      return original unless default.respond_to?(:merge)
+
+      default.merge(original)
+    end
+
     def build_buffer(response, body)
       Buffer.new response, body
     end