diff --git a/tornado/httpclient.py b/tornado/httpclient.py
index 27edf15e..60db3a22 100644
--- a/tornado/httpclient.py
+++ b/tornado/httpclient.py
@@ -57,11 +57,11 @@ class HTTPClient(object):
         except httpclient.HTTPError, e:
             print "Error:", e
     """
-    def __init__(self, async_client_class=None):
+    def __init__(self, async_client_class=None, **kwargs):
         self._io_loop = IOLoop()
         if async_client_class is None:
             async_client_class = AsyncHTTPClient
-        self._async_client = async_client_class(self._io_loop)
+        self._async_client = async_client_class(self._io_loop, **kwargs)
         self._response = None
         self._closed = False