diff --git a/ChangeLog b/ChangeLog
index 65e48cc907..c91921fd56 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Feb  6 23:37:11 2010  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* lib/net/ftp.rb (initialize): set @sock to a NullSocket instance to
+	  raise FTPConnectionError when not connected.   [ruby-dev:40258]
+
 Sat Feb  6 23:25:57 2010  Shugo Maeda  <shugo@ruby-lang.org>
 
 	* ext/curses/view2.rb: replaced with Hugh Sasse's version.
diff --git a/lib/net/ftp.rb b/lib/net/ftp.rb
index 0bf1fb25ca..f393a15bff 100644
--- a/lib/net/ftp.rb
+++ b/lib/net/ftp.rb
@@ -25,6 +25,7 @@ module Net
   class FTPTempError < FTPError; end
   class FTPPermError < FTPError; end
   class FTPProtoError < FTPError; end
+  class FTPConnectionError < FTPError; end
   # :startdoc:
 
   #
@@ -132,7 +133,7 @@ module Net
       @passive = false
       @debug_mode = false
       @resume = false
-      @sock = nil
+      @sock = NullSocket.new
       @logged_in = false
       if host
 	connect(host)
@@ -966,8 +967,15 @@ module Net
       return dirname
     end
     private :parse257
-  end
 
+    # :stopdoc:
+    class NullSocket
+      def method_missing(mid, *args)
+        raise FTPConnectionError, "not connected"
+      end
+    end
+    # :startdoc:
+  end
 end