diff --git a/lib/http/cookie.rb b/lib/http/cookie.rb
index 56eeb91..d675369 100644
--- a/lib/http/cookie.rb
+++ b/lib/http/cookie.rb
@@ -114,9 +114,12 @@ class HTTP::Cookie
   # is called if defined.  Each key can be either a symbol or a
   # string of downcased attribute names.
   #
-  # This methods accepts any attribute name for which a setter method
+  # This method accepts any attribute name for which a setter method
   # is defined.  Beware, however, any error (typically ArgumentError)
-  # a setter method raises will be passed through.
+  # a setter method raises will be passed through.  It is preferred
+  # that each keyword is a downcased symbol.  Support for strings and
+  # mixed case keywords will be obsoleted when ruby 2.0 keyword syntax
+  # is adopted.
   #
   # If `value` is omitted or it is nil, an expiration cookie is
   # created unless `max_age` or `expires` (`expires_at`) is given.
@@ -157,8 +160,8 @@ class HTTP::Cookie
     end
     for_domain = false
     domain = max_age = origin = nil
-    attr_hash.each_pair { |key, val|
-      case key.to_sym
+    attr_hash.each_pair { |okey, val|
+      case key ||= okey
       when :name
         self.name = val
       when :value
@@ -181,7 +184,7 @@ class HTTP::Cookie
       when :secure, :secure?
         @secure = val
       when /[A-Z]/
-        warn "keyword should be downcased: #{key}" if $VERBOSE
+        warn "keyword should be downcased: #{okey.inspect}" if $VERBOSE
         key = key.downcase
         redo
       when Symbol
@@ -189,14 +192,15 @@ class HTTP::Cookie
         if respond_to?(setter)
           __send__(setter, val)
         else
-          warn "unknown keyword: #{key}" if $VERBOSE
+          warn "unknown keyword: #{okey.inspect}" if $VERBOSE
         end
       when String
+        warn "use symbol for keyword: #{okey.inspect}" if $VERBOSE
         key = key.to_sym
         redo
       else
-        key = key.to_s
-        redo
+        warn "invalid keyword ignored: #{okey.inspect}" if $VERBOSE
+        next
       end
     }
     if @name.nil?
diff --git a/lib/http/cookie_jar/yaml_saver.rb b/lib/http/cookie_jar/yaml_saver.rb
index 88354ca..490d6b4 100644
--- a/lib/http/cookie_jar/yaml_saver.rb
+++ b/lib/http/cookie_jar/yaml_saver.rb
@@ -42,7 +42,11 @@ class HTTP::CookieJar::YAMLSaver < HTTP::CookieJar::AbstractSaver
               # YAML::Object of Syck
               cookie_hash = cookie_hash.ivars
             end
-            cookie = HTTP::Cookie.new(cookie_hash)
+            cookie = HTTP::Cookie.new({}.tap { |hash|
+                cookie_hash.each_pair { |key, value|
+                  hash[key.to_sym] = value
+                }
+              })
             jar.add(cookie)
           }
         }
diff --git a/test/helper.rb b/test/helper.rb
index d259cb4..87dd8a0 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -3,6 +3,30 @@ require 'test-unit'
 require 'uri'
 require 'http/cookie'
 
+module Test
+  module Unit
+    module Assertions
+      def assert_warn(pattern, message = nil, &block)
+        class << (output = "")
+          alias write <<
+        end
+        stderr, $stderr = $stderr, output
+        yield
+        assert_match(pattern, output, message)
+      ensure
+        $stderr = stderr
+      end
+
+      def assert_warning(pattern, message = nil, &block)
+        verbose, $VERBOSE = $VERBOSE, true
+        assert_warn(pattern, message, &block)
+      ensure
+        $VERBOSE = verbose
+      end
+    end
+  end
+end
+
 module Enumerable
   def combine
     masks = inject([[], 1]){|(ar, m), e| [ar << m, m << 1 ] }[0]
diff --git a/test/test_http_cookie.rb b/test/test_http_cookie.rb
index 4cf47b5..cfa2a22 100644
--- a/test/test_http_cookie.rb
+++ b/test/test_http_cookie.rb
@@ -2,13 +2,6 @@
 require File.expand_path('helper', File.dirname(__FILE__))
 
 class TestHTTPCookie < Test::Unit::TestCase
-  def silently
-    warn_level, $VERBOSE = $VERBOSE, false
-    yield
-  ensure
-    $VERBOSE = warn_level
-  end
-
   def setup
     httpdate = 'Sun, 27-Sep-2037 00:00:00 GMT'
 
@@ -46,12 +39,10 @@ class TestHTTPCookie < Test::Unit::TestCase
 
     dates.each do |date|
       cookie = "PREF=1; expires=#{date}"
-      silently do
-        assert_equal 1, HTTP::Cookie.parse(cookie, url) { |c|
-          assert c.expires, "Tried parsing: #{date}"
-          assert_send [c.expires, :<, yesterday]
-        }.size
-      end
+      assert_equal 1, HTTP::Cookie.parse(cookie, url) { |c|
+        assert c.expires, "Tried parsing: #{date}"
+        assert_send [c.expires, :<, yesterday]
+      }.size
     end
 
     [
@@ -177,14 +168,12 @@ class TestHTTPCookie < Test::Unit::TestCase
       "20/06/95 21:07",
     ]
 
-    silently do
-      dates.each do |date|
-        cookie = "PREF=1; expires=#{date}"
-        assert_equal 1, HTTP::Cookie.parse(cookie, url) { |c|
-          assert_equal(true, c.expires.nil?)
-        }.size
-      end
-    end
+    dates.each { |date|
+      cookie = "PREF=1; expires=#{date}"
+      assert_equal 1, HTTP::Cookie.parse(cookie, url) { |c|
+        assert_equal(true, c.expires.nil?)
+      }.size
+    }
   end
 
   def test_parse_domain_dot
@@ -537,6 +526,30 @@ class TestHTTPCookie < Test::Unit::TestCase
       cookie.acceptable?
     }
 
+    # various keywords
+    [
+      [:Expires,  /should be downcased/],
+      ["Expires", /should be downcased.*use symbol/m],
+    ].each { |key, pattern|
+      assert_warning(pattern, "warn of key: #{key.inspect}") {
+        cookie = HTTP::Cookie.new(:value => 'value', :name => 'key', key => expires.dup)
+        assert_equal 'key', cookie.name
+        assert_equal 'value', cookie.value
+        assert_equal expires, cookie.expires
+      }
+    }
+    [
+      [:expires?, /unknown keyword/],
+      [[:expires], /invalid keyword/],
+    ].each { |key, pattern|
+      assert_warning(pattern, "warn of key: #{key.inspect}") {
+        cookie = HTTP::Cookie.new(:value => 'value', :name => 'key', key => expires.dup)
+        assert_equal 'key', cookie.name
+        assert_equal 'value', cookie.value
+        assert_equal nil, cookie.expires
+      }
+    }
+
     cookie = HTTP::Cookie.new(:value => 'value', :name => 'key', :expires => expires.dup)
     assert_equal 'key', cookie.name
     assert_equal 'value', cookie.value