diff --git a/ChangeLog b/ChangeLog
index 188f2fa714..644f921d5e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Feb  8 09:41:47 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* runruby.rb: gets extout and arch from rbconfig.rb.
+
 Sat Feb  7 21:26:15 2009  Tanaka Akira  <akr@fsij.org>
 
 	* test/socket/test_addrinfo.rb (test_family_addrinfo): don't use
diff --git a/runruby.rb b/runruby.rb
index b2a8802be1..2bddf634ed 100755
--- a/runruby.rb
+++ b/runruby.rb
@@ -49,9 +49,10 @@ unless File.exist?(ruby)
 end
 
 libs = [abs_archdir]
+extout ||= config["EXTOUT"]
 if extout
   abs_extout = File.expand_path(extout)
-  libs << File.expand_path("common", abs_extout) << File.expand_path(RUBY_PLATFORM, abs_extout)
+  libs << File.expand_path("common", abs_extout) << File.expand_path(config['arch'], abs_extout)
 end
 libs << File.expand_path("lib", srcdir)
 config["bindir"] = abs_archdir