diff --git a/ChangeLog b/ChangeLog
index af65c3178d..d9626f1b80 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Jul  7 11:02:55 2014  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* tool/mkconfig.rb: remove not to require rbconfig/obsolete.rb.
+
+	* lib/rbconfig/obsolete.rb: removed.
+
 Mon Jul  7 10:52:03 2014  Koichi Sasada  <ko1@atdot.net>
 
 	* parse.y: do not use rb_gc_resurrect(), but create a new dynamic
diff --git a/lib/rbconfig/obsolete.rb b/lib/rbconfig/obsolete.rb
deleted file mode 100644
index 52bc5c20d4..0000000000
--- a/lib/rbconfig/obsolete.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-module ::RbConfig
-  module Obsolete
-  end
-  class << Obsolete
-    def _warn_
-      loc, = caller_locations(2, 1)
-      loc = "#{loc}: " if loc
-      warn "#{loc}Use RbConfig instead of obsolete and deprecated Config."
-      self
-    end
-
-    def const_missing(name)
-      _warn_
-      ::RbConfig.const_get(name)
-    end
-
-    def method_missing(*args, &block)
-      _warn_
-      rbconfig = ::RbConfig
-      result = rbconfig.__send__(*args, &block)
-      result = rbconfig if rbconfig.equal?(result)
-      result
-    end
-
-    def respond_to_missing?(*args, &block)
-      _warn_
-      ::RbConfig.send(:respond_to_missing?, *args, &block)
-    end
-  end
-end
-
-::Config = ::RbConfig::Obsolete._warn_
-=begin
-def Object.const_missing(name)
-  return super unless name == :Config
-  ::RbConfig::Obsolete._warn_
-end
-=end
diff --git a/tool/mkconfig.rb b/tool/mkconfig.rb
index 85b5ca45a5..3da57581ee 100755
--- a/tool/mkconfig.rb
+++ b/tool/mkconfig.rb
@@ -267,7 +267,6 @@ print <<EOS
     )
   end
 end
-autoload :Config, "rbconfig/obsolete.rb" # compatibility for ruby-1.8.4 and older.
 CROSS_COMPILING = nil unless defined? CROSS_COMPILING
 EOS