diff --git a/ChangeLog b/ChangeLog
index 2607bc1037..9ed4304ad3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,13 @@ Sat Apr 12 12:41:49 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 	  parser_warn, e_option_supplied, warn_unless_e_option, range_op,
 	  cond0): nd_file is no longer used.
 
+Sat Apr 12 12:17:31 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* prelude.rb (require_relative): move require_relative from
+	  lib/require_relative.rb.  [ruby-core:16356]
+
+	* lib/require_relative.rb: removed.
+
 Sat Apr 12 05:55:57 2008  Eric Hodel  <drbrain@segment7.net>
 
 	* lib/rubygems*, test/rubygems*:  Update to RubyGems 1.1.1 r1701.
diff --git a/lib/require_relative.rb b/lib/require_relative.rb
deleted file mode 100644
index e68546f1ce..0000000000
--- a/lib/require_relative.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-def require_relative(relative_feature)
-  c = caller.first
-  e = c.rindex(/:\d+:in /)
-  file = $`
-  if /\A\((.*)\)/ =~ file # eval, etc.
-    raise LoadError, "require_relative is called in #{$1}"
-  end
-  absolute_feature = File.expand_path(File.join(File.dirname(file), relative_feature))
-  require absolute_feature
-end
-
diff --git a/prelude.rb b/prelude.rb
index a38a578595..fdf401b56a 100644
--- a/prelude.rb
+++ b/prelude.rb
@@ -23,3 +23,13 @@ class Thread
   end
 end
 
+def require_relative(relative_feature)
+  c = caller.first
+  e = c.rindex(/:\d+:in /)
+  file = $`
+  if /\A\((.*)\)/ =~ file # eval, etc.
+    raise LoadError, "require_relative is called in #{$1}"
+  end
+  absolute_feature = File.expand_path(File.join(File.dirname(file), relative_feature))
+  require absolute_feature
+end
diff --git a/test/ruby/test_assignment.rb b/test/ruby/test_assignment.rb
index 2b22613c55..b82cee81d1 100644
--- a/test/ruby/test_assignment.rb
+++ b/test/ruby/test_assignment.rb
@@ -490,7 +490,6 @@ class TestAssignment < Test::Unit::TestCase
   end
 end
 
-require 'require_relative'
 require_relative 'sentence'
 class TestAssignmentGen < Test::Unit::TestCase
   Syntax = {
diff --git a/test/ruby/test_beginendblock.rb b/test/ruby/test_beginendblock.rb
index 2f6a5437f3..f75311f3b0 100644
--- a/test/ruby/test_beginendblock.rb
+++ b/test/ruby/test_beginendblock.rb
@@ -1,6 +1,5 @@
 require 'test/unit'
 require 'tempfile'
-require 'require_relative'
 require_relative 'envutil'
 
 class TestBeginEndBlock < Test::Unit::TestCase
diff --git a/test/ruby/test_file.rb b/test/ruby/test_file.rb
index 62e1c6341a..22dc1a89e5 100644
--- a/test/ruby/test_file.rb
+++ b/test/ruby/test_file.rb
@@ -1,6 +1,5 @@
 require 'test/unit'
 require 'tempfile'
-require 'require_relative'
 require_relative 'ut_eof'
 
 class TestFile < Test::Unit::TestCase
diff --git a/test/ruby/test_m17n_comb.rb b/test/ruby/test_m17n_comb.rb
index ca527cc807..26efa85ea2 100644
--- a/test/ruby/test_m17n_comb.rb
+++ b/test/ruby/test_m17n_comb.rb
@@ -1,6 +1,5 @@
 require 'test/unit'
 require 'stringio'
-require 'require_relative'
 require_relative 'allpairs'
 
 class TestM17NComb < Test::Unit::TestCase
diff --git a/test/ruby/test_marshal.rb b/test/ruby/test_marshal.rb
index ce9882b5e8..3979e8a15f 100644
--- a/test/ruby/test_marshal.rb
+++ b/test/ruby/test_marshal.rb
@@ -1,5 +1,4 @@
 require 'test/unit'
-require 'require_relative'
 require_relative 'marshaltestlib'
 
 class TestMarshal < Test::Unit::TestCase
diff --git a/test/ruby/test_pipe.rb b/test/ruby/test_pipe.rb
index 3b47bdee53..34f231ad8c 100644
--- a/test/ruby/test_pipe.rb
+++ b/test/ruby/test_pipe.rb
@@ -1,5 +1,4 @@
 require 'test/unit'
-require 'require_relative'
 require_relative 'ut_eof'
 
 class TestPipe < Test::Unit::TestCase
diff --git a/test/ruby/test_sprintf_comb.rb b/test/ruby/test_sprintf_comb.rb
index 667ceab849..8b2c1a7e05 100644
--- a/test/ruby/test_sprintf_comb.rb
+++ b/test/ruby/test_sprintf_comb.rb
@@ -1,5 +1,4 @@
 require 'test/unit'
-require 'require_relative'
 require_relative 'allpairs'
 
 class TestSprintfComb < Test::Unit::TestCase
diff --git a/test/ruby/test_system.rb b/test/ruby/test_system.rb
index 9a897027bf..ec8aca74cb 100644
--- a/test/ruby/test_system.rb
+++ b/test/ruby/test_system.rb
@@ -1,6 +1,5 @@
 require 'test/unit'
 require 'tmpdir'
-require 'require_relative'
 require_relative 'envutil'
 
 class TestSystem < Test::Unit::TestCase
diff --git a/test/ruby/test_yield.rb b/test/ruby/test_yield.rb
index e1169f5d51..452c17b141 100644
--- a/test/ruby/test_yield.rb
+++ b/test/ruby/test_yield.rb
@@ -74,7 +74,6 @@ class TestRubyYield < Test::Unit::TestCase
   end
 end
 
-require 'require_relative'
 require_relative 'sentence'
 class TestRubyYieldGen < Test::Unit::TestCase
   Syntax = {