diff -r 0109092fc9e9 configure
--- a/configure	Mon Sep 05 17:22:24 2016 -0700
+++ b/configure	Tue Sep 06 17:49:09 2016 +0000
@@ -9964,12 +9964,12 @@
 $as_echo "$with_system_expat" >&6; }
 
 # Check for use of the system libffi library
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-system-ffi" >&5
-$as_echo_n "checking for --with-system-ffi... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --without-system-ffi" >&5
+$as_echo_n "checking for --without-system-ffi... " >&6; }
 
 # Check whether --with-system_ffi was given.
 if test "${with_system_ffi+set}" = set; then :
-  withval=$with_system_ffi;
+  withval=$with_system_ffi; with_system_ffi="yes"
 else
   with_system_ffi="no"
 fi
diff -r 0109092fc9e9 configure.ac
--- a/configure.ac	Mon Sep 05 17:22:24 2016 -0700
+++ b/configure.ac	Tue Sep 06 17:49:09 2016 +0000
@@ -2722,10 +2722,10 @@
 AC_MSG_RESULT($with_system_expat)
 
 # Check for use of the system libffi library
-AC_MSG_CHECKING(for --with-system-ffi)
+AC_MSG_CHECKING(for --without-system-ffi)
 AC_ARG_WITH(system_ffi,
             AS_HELP_STRING([--with-system-ffi], [build _ctypes module using an installed ffi library]),
-            [],
+            [with_system_ffi="yes"],
             [with_system_ffi="no"])
 
 if test "$with_system_ffi" = "yes" && test -n "$PKG_CONFIG"; then
diff -r 0109092fc9e9 setup.py
--- a/setup.py	Mon Sep 05 17:22:24 2016 -0700
+++ b/setup.py	Tue Sep 06 17:49:09 2016 +0000
@@ -1888,6 +1888,9 @@
             if host_platform == 'darwin':
                 return self.configure_ctypes_darwin(ext)
 
+            print('warning: building with the bundled copy of libffi is'
+                  ' deprecated on this platform.  It will not be'
+                  ' distributed with Python 3.7')
             srcdir = sysconfig.get_config_var('srcdir')
             ffi_builddir = os.path.join(self.build_temp, 'libffi')
             ffi_srcdir = os.path.abspath(os.path.join(srcdir, 'Modules',
@@ -1984,7 +1987,7 @@
                      libraries=math_libs)
         self.extensions.extend([ext, ext_test])
 
-        if not '--with-system-ffi' in sysconfig.get_config_var("CONFIG_ARGS"):
+        if '--without-system-ffi' in sysconfig.get_config_var("CONFIG_ARGS"):
             return
 
         if host_platform == 'darwin':