diff --git a/src/calibre/srv/loop.py b/src/calibre/srv/loop.py
index 95993c16cc..0a15cc1167 100644
--- a/src/calibre/srv/loop.py
+++ b/src/calibre/srv/loop.py
@@ -15,13 +15,12 @@ from calibre.ptempfile import TemporaryDirectory
 from calibre.srv.opts import Options
 from calibre.srv.utils import (
     socket_errors_socket_closed, socket_errors_nonblocking, HandleInterrupt,
-    socket_errors_eintr, start_cork, stop_cork)
+    socket_errors_eintr, start_cork, stop_cork, DESIRED_SEND_BUFFER_SIZE)
 from calibre.utils.socket_inheritance import set_socket_inherit
 from calibre.utils.logging import ThreadSafeLog
 from calibre.utils.monotonic import monotonic
 
 READ, WRITE, RDWR = 'READ', 'WRITE', 'RDWR'
-DESIRED_SEND_BUFFER_SIZE = 16 * 1024
 
 class Connection(object):
 
diff --git a/src/calibre/srv/tests/http.py b/src/calibre/srv/tests/http.py
index c4e4d6daaf..d1d5c2cc34 100644
--- a/src/calibre/srv/tests/http.py
+++ b/src/calibre/srv/tests/http.py
@@ -329,6 +329,7 @@ class TestHTTP(BaseTest):
                 self.ae(len(data), len(rdata))
                 self.ae(hashlib.sha1(data).hexdigest(), hashlib.sha1(rdata).hexdigest())
                 self.ae(data, rdata)
-                self.assertLess(monotonic() - start_time, 1, 'Large file transfer took too long')
+                time_taken = monotonic() - start_time
+                self.assertLess(time_taken, 1, 'Large file transfer took too long')
 
     # }}}
diff --git a/src/calibre/srv/utils.py b/src/calibre/srv/utils.py
index cb6602db69..174addfa70 100644
--- a/src/calibre/srv/utils.py
+++ b/src/calibre/srv/utils.py
@@ -17,6 +17,7 @@ from calibre.constants import iswindows
 
 HTTP1  = 'HTTP/1.0'
 HTTP11 = 'HTTP/1.1'
+DESIRED_SEND_BUFFER_SIZE = 16 * 1024  # windows 7 uses an 8KB sndbuf
 
 def http_date(timeval=None):
     return type('')(formatdate(timeval=timeval, usegmt=True))