--- extconf.rb~	2017-10-05 20:21:59.480315863 +0200

+++ extconf.rb	2017-10-05 20:23:55.077931560 +0200

@@ -6,12 +6,7 @@

 require 'mkmf'

 require 'rbconfig'

-

-$CFLAGS = case RUBY_VERSION

-          when /^1\.9/; '-DRUBY19'

-          when /^2\./; '-DRUBY19'

-          else; ''

-          end

+$CFLAGS = "#{$CFLAGS} -DRUBY19"

 implementation = case CONFIG['host_os']

                  when /linux/i; 'shadow'