diff -urN a/setup.py b/setup.py
--- a/setup.py	2014-10-11 14:20:05.461046200 +0100
+++ b/setup.py	2014-10-11 14:20:08.299208600 +0100
@@ -1512,7 +1512,7 @@
             macros = dict()
             libraries = ['rt']
 
-        if host_platform == 'win32':
+        if host_platform.startswith(('mingw', 'win')):
             multiprocessing_srcs = [ '_multiprocessing/multiprocessing.c',
                                      '_multiprocessing/semaphore.c',
                                    ]
@@ -1525,8 +1525,12 @@
                 multiprocessing_srcs.append('_multiprocessing/semaphore.c')
 
         if sysconfig.get_config_var('WITH_THREAD'):
+            multiprocessing_libs = []
+            if host_platform.startswith(('mingw', 'win')):
+                multiprocessing_libs += ['ws2_32']
             exts.append ( Extension('_multiprocessing', multiprocessing_srcs,
                                     define_macros=list(macros.items()),
+                                    libraries=multiprocessing_libs,
                                     include_dirs=["Modules/_multiprocessing"]))
         else:
             missing.append('_multiprocessing')