diff --git a/CHANGELOG.md b/CHANGELOG.md
index dbdb5cad7..b7ccdf964 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,7 @@ All notable changes to this project will be documented in this file. For info on
 
 ### Fixed
 
+- Make Rack::MockResponse handle non-hash headers. ([#1629](https://github.com/rack/rack/issues/1629), [@jeremyevans](https://github.com/jeremyevans))
 - TempfileReaper now deletes temp files if application raises an exception. ([#1679](https://github.com/rack/rack/issues/1679), [@jeremyevans](https://github.com/jeremyevans))
 - Fix using Rack::Session::Cookie with coder: Rack::Session::Cookie::Base64::{JSON,Zip}. ([#1666](https://github.com/rack/rack/issues/1666), [@jeremyevans](https://github.com/jeremyevans))
 - Avoid NoMethodError when accessing Rack::Session::Cookie without requiring delegate first. ([#1610](https://github.com/rack/rack/issues/1610), [@onigra](https://github.com/onigra))
diff --git a/lib/rack/mock.rb b/lib/rack/mock.rb
index f330ae18f..14ee7f0bc 100644
--- a/lib/rack/mock.rb
+++ b/lib/rack/mock.rb
@@ -184,10 +184,10 @@ class << self
     def initialize(status, headers, body, errors = StringIO.new(""))
       @original_headers = headers
       @errors           = errors.string if errors.respond_to?(:string)
-      @cookies = parse_cookies_from_header
 
       super(body, status, headers)
 
+      @cookies = parse_cookies_from_header
       buffered_body!
     end
 
@@ -231,8 +231,8 @@ def cookie(name)
 
     def parse_cookies_from_header
       cookies = Hash.new
-      if original_headers.has_key? 'Set-Cookie'
-        set_cookie_header = original_headers.fetch('Set-Cookie')
+      if headers.has_key? 'Set-Cookie'
+        set_cookie_header = headers.fetch('Set-Cookie')
         set_cookie_header.split("\n").each do |cookie|
           cookie_name, cookie_filling = cookie.split('=', 2)
           cookie_attributes = identify_cookie_attributes cookie_filling
diff --git a/test/spec_mock.rb b/test/spec_mock.rb
index 43fd07d19..bce1cd201 100644
--- a/test/spec_mock.rb
+++ b/test/spec_mock.rb
@@ -330,6 +330,21 @@
     res.cookie("i_dont_exist").must_be_nil
   end
 
+  it "parses cookie headers provided as an array" do
+    res = Rack::MockRequest.new(->(env) { [200, [["set-cookie", "array=awesome"]], [""]] }).get("")
+    array_cookie = res.cookie("array")
+    array_cookie.value[0].must_equal "awesome"
+  end
+
+  it "parses multiple set-cookie headers provided as an array" do
+    cookie_headers = [["set-cookie", "array=awesome\nmultiple=times"]]
+    res = Rack::MockRequest.new(->(env) { [200, cookie_headers, [""]] }).get("")
+    array_cookie = res.cookie("array")
+    array_cookie.value[0].must_equal "awesome"
+    second_cookie = res.cookie("multiple")
+    second_cookie.value[0].must_equal "times"
+  end
+
   it "provide access to the HTTP body" do
     res = Rack::MockRequest.new(app).get("")
     res.body.must_match(/rack/)
@@ -346,6 +361,12 @@
     res.errors.must_include "foo"
   end
 
+  it "handle enumerable headers that are not a hash" do
+    # this is exactly what rack-test does
+    res = Rack::MockResponse.new(200, [], [])
+    res.cookies.must_equal({})
+  end
+
   it "allow calling body.close afterwards" do
     # this is exactly what rack-test does
     body = StringIO.new("hi")