--- ./ext/trace_nums/extconf.rb.debug	1970-01-01 09:00:00.000000000 +0900
+++ ./ext/trace_nums/extconf.rb	2012-04-30 18:02:37.000000000 +0900
@@ -1,5 +1,4 @@
 require "mkmf"
-require "ruby_core_source"
 
 if RUBY_VERSION >= "1.8"
   if RUBY_RELEASE_DATE < "2005-03-22"
@@ -16,7 +15,10 @@
 }
 
 dir_config("ruby")
-if !Ruby_core_source::create_makefile_with_core(hdrs, "trace_nums19")
+#if !Ruby_core_source::create_makefile_with_core(hdrs, "trace_nums19")
+if hdrs.call
+  create_makefile("trace_nums19")
+else
   STDERR.print("Makefile creation failed\n")
   STDERR.print("*************************************************************\n\n")
   STDERR.print("  NOTE: For Ruby 1.9 installation instructions, please see:\n\n")