diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index e6ed28742f..9cfe5a5ea9 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -43,7 +43,8 @@ module ActionDispatch # :nodoc:
         @block = nil
         @length = 0
 
-        @status, @header, @body = status, header, body
+        @status, @header = status, header
+        self.body = body
 
         @cookie = []
         @sending_file = false