--- a/Lib/distutils/sysconfig.py	2019-10-19 20:38:44.000000000 +0200
+++ b/Lib/distutils/sysconfig.py	2019-03-02 19:17:42.000000000 +0100
@@ -181,8 +171,8 @@
                 _osx_support.customize_compiler(_config_vars)
                 _config_vars['CUSTOMIZED_OSX_COMPILER'] = 'True'
 
-        (cc, cxx, cflags, ccshared, ldshared, so_ext, ar, ar_flags) = \
-            get_config_vars('CC', 'CXX', 'CFLAGS',
+        (cc, cxx, opt, cflags, ccshared, ldshared, so_ext, ar, ar_flags) = \
+            get_config_vars('CC', 'CXX', 'OPT', 'CFLAGS',
                             'CCSHARED', 'LDSHARED', 'SO', 'AR',
                             'ARFLAGS')
 
@@ -206,7 +196,7 @@
         if 'LDFLAGS' in os.environ:
             ldshared = ldshared + ' ' + os.environ['LDFLAGS']
         if 'CFLAGS' in os.environ:
-            cflags = cflags + ' ' + os.environ['CFLAGS']
+            cflags = opt + ' ' + os.environ['CFLAGS']
             ldshared = ldshared + ' ' + os.environ['CFLAGS']
         if 'CPPFLAGS' in os.environ:
             cpp = cpp + ' ' + os.environ['CPPFLAGS']