diff --git a/ChangeLog b/ChangeLog
index 951a4a076d..fd0a8236cc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Apr 24 21:43:58 2012  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* lib/net/smtp.rb (check_continue): raise an error with an explanatory
+	  message.  [ruby-core:35854] [Feature #4598]
+
 Tue Apr 24 21:11:31 2012  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* lib/optparse.rb (OptionParser#to_a): should split by end-of-line,
diff --git a/lib/net/smtp.rb b/lib/net/smtp.rb
index feab4b3a0b..27d4557c0e 100644
--- a/lib/net/smtp.rb
+++ b/lib/net/smtp.rb
@@ -955,7 +955,7 @@ module Net
 
     def check_continue(res)
       unless res.continue?
-        raise SMTPUnknownError, "could not get 3xx (#{res.status})"
+        raise SMTPUnknownError, "could not get 3xx (#{res.status}: #{res.string})"
       end
     end