add 'no' output to --with-system-ffi
diff --git a/configure.in b/configure.in
index 2863b8d..15105e7 100644
--- a/configure.in
+++ b/configure.in
@@ -1995,7 +1995,9 @@
 # Check for use of the system libffi library
 AC_MSG_CHECKING(for --with-system-ffi)
 AC_ARG_WITH(system_ffi,
-            AC_HELP_STRING(--with-system-ffi, build _ctypes module using an installed ffi library))
+            AC_HELP_STRING(--with-system-ffi, build _ctypes module using an installed ffi library),
+            [],
+            [with_system_ffi="no"])
 
 AC_MSG_RESULT($with_system_ffi)