diff --git a/lib/http/cookie.rb b/lib/http/cookie.rb
index fea518f..b8cf906 100644
--- a/lib/http/cookie.rb
+++ b/lib/http/cookie.rb
@@ -503,7 +503,7 @@ class HTTP::Cookie
 
   # Expires this cookie by setting the expires attribute value to a
   # past date.
-  def expire
+  def expire!
     self.expires = UNIX_EPOCH
     self
   end
diff --git a/lib/http/cookie_jar/hash_store.rb b/lib/http/cookie_jar/hash_store.rb
index 76a35da..9d59801 100644
--- a/lib/http/cookie_jar/hash_store.rb
+++ b/lib/http/cookie_jar/hash_store.rb
@@ -114,7 +114,7 @@ class HTTP::CookieJar
         if (debt = domain_cookies.size - HTTP::Cookie::MAX_COOKIES_PER_DOMAIN) > 0
           domain_cookies.sort_by!(&:created_at)
           domain_cookies.slice!(0, debt).each { |cookie|
-            add(cookie.expire)
+            add(cookie.expire!)
           }
         end
 
@@ -124,7 +124,7 @@ class HTTP::CookieJar
       if (debt = all_cookies.size - HTTP::Cookie::MAX_COOKIES_TOTAL) > 0
         all_cookies.sort_by!(&:created_at)
         all_cookies.slice!(0, debt).each { |cookie|
-          add(cookie.expire)
+          add(cookie.expire!)
         }
       end
 
diff --git a/test/test_http_cookie.rb b/test/test_http_cookie.rb
index 93b3cee..f68d9e4 100644
--- a/test/test_http_cookie.rb
+++ b/test/test_http_cookie.rb
@@ -514,7 +514,7 @@ class TestHTTPCookie < Test::Unit::TestCase
     assert_equal false, cookie.expired?
     assert_equal true, cookie.expired?(cookie.expires + 1)
     assert_equal false, cookie.expired?(cookie.expires - 1)
-    cookie.expire
+    cookie.expire!
     assert_equal true, cookie.expired?
   end