diff -rupN PyQt5_gpl-5.12.3/configure.py PyQt5_gpl-5.12.3-new/configure.py
--- PyQt5_gpl-5.12.3/configure.py	2019-06-25 14:40:51.000000000 +0200
+++ PyQt5_gpl-5.12.3-new/configure.py	2019-07-18 16:43:50.119391496 +0200
@@ -2629,7 +2629,7 @@ 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@@', ' '.join(sip_flags))
+            line = line.replace('@@PYQT_SIP_FLAGS@@', ' '.join(sip_flags).replace("WS_X11", "WS_WIN"))
             out_f.write(line)
 
         in_f.close()