diff --git a/Lib/httplib.py b/Lib/httplib.py
index f299873..d7254ff 100644
--- a/Lib/httplib.py
+++ b/Lib/httplib.py
@@ -410,7 +410,7 @@
                 self.close()
             raise
 
-    def putrequest(self, method, url):
+    def putrequest(self, method, url, skip_host=0):
         """Send a request to the server.
 
         `method' specifies an HTTP request method, e.g. 'GET'.
@@ -461,24 +461,31 @@
         if self._http_vsn == 11:
             # Issue some standard headers for better HTTP/1.1 compliance
 
-            # this header is issued *only* for HTTP/1.1 connections. more
-            # specifically, this means it is only issued when the client uses
-            # the new HTTPConnection() class. backwards-compat clients will
-            # be using HTTP/1.0 and those clients may be issuing this header
-            # themselves. we should NOT issue it twice; some web servers (such
-            # as Apache) barf when they see two Host: headers
+            if not skip_host:
+                # this header is issued *only* for HTTP/1.1
+                # connections. more specifically, this means it is
+                # only issued when the client uses the new
+                # HTTPConnection() class. backwards-compat clients
+                # will be using HTTP/1.0 and those clients may be
+                # issuing this header themselves. we should NOT issue
+                # it twice; some web servers (such as Apache) barf
+                # when they see two Host: headers
 
-            # If we need a non-standard port,include it in the header.
-            # If the request is going through a proxy, but the host of
-            # the actual URL, not the host of the proxy.
+                # If we need a non-standard port,include it in the
+                # header.  If the request is going through a proxy,
+                # but the host of the actual URL, not the host of the
+                # proxy.
 
-            if url.startswith('http:'):
-                nil, netloc, nil, nil, nil = urlsplit(url)
-                self.putheader('Host', netloc)
-            elif self.port == HTTP_PORT:
-                self.putheader('Host', netloc)
-            else:
-                self.putheader('Host', "%s:%s" % (self.host, self.port))
+                netloc = ''
+                if url.startswith('http'):
+                    nil, netloc, nil, nil, nil = urlsplit(url)
+
+                if netloc:
+                    self.putheader('Host', netloc)
+                elif self.port == HTTP_PORT:
+                    self.putheader('Host', self.host)
+                else:
+                    self.putheader('Host', "%s:%s" % (self.host, self.port))
 
             # note: we are assuming that clients will not attempt to set these
             #       headers since *this* library must deal with the
@@ -536,7 +543,14 @@
             self._send_request(method, url, body, headers)
 
     def _send_request(self, method, url, body, headers):
-        self.putrequest(method, url)
+        # If headers already contains a host header, then define the
+        # optional skip_host argument to putrequest().  The check is
+        # harder because field names are case insensitive.
+        if (headers.has_key('Host')
+            or [k for k in headers.iterkeys() if k.lower() == "host"]):
+            self.putrequest(method, url, skip_host=1)
+        else:
+            self.putrequest(method, url)
 
         if body:
             self.putheader('Content-Length', str(len(body)))