diff --git a/ChangeLog b/ChangeLog
index 415e99ca5b..e05064ce06 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Nov 16 09:45:23 2003  Minero Aoki  <aamine@loveruby.net>
+
+	* lib/net/http.rb (set_debug_output): warn if method is called
+	  after #start.  [ruby-dev:38798]
+
 Sun Nov 16 04:41:33 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* eval.c (eval): do not re-raise exception to avoid unnecessary
diff --git a/lib/net/http.rb b/lib/net/http.rb
index 684e55f8db..33febdd7ae 100644
--- a/lib/net/http.rb
+++ b/lib/net/http.rb
@@ -366,6 +366,7 @@ module Net # :nodoc:
     #   http.start { .... }
     #
     def set_debug_output( output )
+      warn 'Net::HTTP#set_debug_output called after HTTP started'
       @debug_output = output
     end