--- ./ext/ruby_debug/extconf.rb.debug	1970-01-01 09:00:00.000000000 +0900
+++ ./ext/ruby_debug/extconf.rb	2012-04-30 22:21:21.000000000 +0900
@@ -1,5 +1,4 @@
 require "mkmf"
-require "ruby_core_source"
 
 if RUBY_VERSION < "1.9"
   STDERR.print("Ruby version is too old\n")
@@ -29,7 +28,10 @@
 }
 
 dir_config("ruby")
-if !Ruby_core_source::create_makefile_with_core(hdrs, "ruby_debug")
+#if !Ruby_core_source::create_makefile_with_core(hdrs, "ruby_debug")
+if hdrs.call
+  create_makefile("ruby_debug")
+else
   STDERR.print("Makefile creation failed\n")
   STDERR.print("*************************************************************\n\n")
   STDERR.print("  NOTE: For Ruby 1.9 installation instructions, please see:\n\n")