diff --git a/ChangeLog b/ChangeLog
index 063febbb5d..e997096679 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,13 @@
+Thu Nov 15 17:28:21 2007  Tanaka Akira  <akr@fsij.org>
+
+	* tool/compile_prelude.rb: absolute path may not start with a slash.
+	  pointed by usa.
+
 Thu Nov 15 17:07:54 2007  Tanaka Akira  <akr@fsij.org>
 
 	* tool/compile_prelude.rb: fix first substitution.
 	  use constant for prefix.
+	  pointed by Richard Kilmer.
 
 Thu Nov 15 14:29:56 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
diff --git a/tool/compile_prelude.rb b/tool/compile_prelude.rb
index 4d08b4d68a..314c98689e 100644
--- a/tool/compile_prelude.rb
+++ b/tool/compile_prelude.rb
@@ -33,8 +33,8 @@ lines_list = preludes.map {|filename|
       unless mkconf
         require 'rbconfig'
         mkconf = RbConfig::MAKEFILE_CONFIG.merge('prefix'=>'#{TMP_RUBY_PREFIX}')
-        exlen = $:.grep(%r{\A/}).last.length - RbConfig::CONFIG["prefix"].length
-        setup_ruby_prefix = "TMP_RUBY_PREFIX = $:.grep(%r{\\A/}).last[0..#{-exlen-1}]\n"
+        exlen = $:.reverse.find{|e|e!="."}.length - RbConfig::CONFIG["prefix"].length
+        setup_ruby_prefix = "TMP_RUBY_PREFIX = $:.reverse.find{|e|e!=\".\"}[0..#{-exlen-1}]\n"
         teardown_ruby_prefix = 'Object.class_eval { remove_const "TMP_RUBY_PREFIX" }'
       end
       if RbConfig::MAKEFILE_CONFIG.has_key? key