diff -rupN PyQt5_gpl-5.9.1/configure.py PyQt5_gpl-5.9.1-new/configure.py
--- PyQt5_gpl-5.9.1/configure.py	2017-11-05 16:43:21.698543408 +0100
+++ PyQt5_gpl-5.9.1-new/configure.py	2017-11-05 16:43:21.700543405 +0100
@@ -2486,7 +2486,7 @@ def generate_sip_module_code(target_conf
                 os.path.join('QtCore', 'qpycore_post_init.cpp'))
 
         for line in in_f:
-            line = line.replace('@@PYQT_SIP_FLAGS@@', sip_flags)
+            line = line.replace('@@PYQT_SIP_FLAGS@@', sip_flags.replace("WS_X11", "WS_WIN"))
             out_f.write(line)
 
         in_f.close()