diff --git a/tornado/httpclient.py b/tornado/httpclient.py
index 23496d7b..963aa91a 100644
--- a/tornado/httpclient.py
+++ b/tornado/httpclient.py
@@ -257,7 +257,7 @@ class AsyncHTTPClient(object):
 class HTTPRequest(object):
     def __init__(self, url, method="GET", headers={}, body=None,
                  auth_username=None, auth_password=None,
-                 connect_timeout=None, request_timeout=None,
+                 connect_timeout=20.0, request_timeout=20.0,
                  if_modified_since=None, follow_redirects=True,
                  max_redirects=5, user_agent=None, use_gzip=True,
                  network_interface=None, streaming_callback=None):
@@ -273,8 +273,8 @@ class HTTPRequest(object):
         self.body = body
         self.auth_username = _utf8(auth_username)
         self.auth_password = _utf8(auth_password)
-        self.connect_timeout = connect_timeout or 20.0
-        self.request_timeout = request_timeout or 20.0
+        self.connect_timeout = connect_timeout
+        self.request_timeout = request_timeout
         self.follow_redirects = follow_redirects
         self.max_redirects = max_redirects
         self.user_agent = user_agent