diff --git a/ChangeLog b/ChangeLog
index 1a4db75563..14bd67fdb6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri May 18 15:54:07 2012  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* ext/zlib/extconf.rb: Use an exception instaed of bare puts.
+
 Fri May 18 15:53:05 2012  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* ext/psych/extconf.rb: Use an exception instaed of bare abort.
diff --git a/ext/zlib/extconf.rb b/ext/zlib/extconf.rb
index d94fea743b..d710226f9c 100644
--- a/ext/zlib/extconf.rb
+++ b/ext/zlib/extconf.rb
@@ -48,8 +48,7 @@ if %w'z libz zlib1 zlib zdll'.find {|z| have_library(z, 'deflateReset')} and
     'OS_UNKNOWN' => 'Unknown',
   }
   unless OS_NAMES.key? os_code then
-    puts "invalid OS_CODE `#{os_code}'"
-    exit
+    raise "invalid OS_CODE `#{os_code}'"
   end
   message "#{OS_NAMES[os_code]}\n"
   defines << "OS_CODE=#{os_code}"