diff --git a/ChangeLog b/ChangeLog
index 18becd871a..e533338d30 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Jul  7 17:12:20 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/ipaddr.rb (IPAddr#initialize): get rid of ArgumentError in
+	  IPAddr#to_range.  a patch from okkez <okkez000 AT gmail.com> in
+	  [ruby-dev:35091].
+
 Mon Jul  7 01:24:43 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* file.c (rb_file_s_extname): fix for file name with spaces.
diff --git a/lib/ipaddr.rb b/lib/ipaddr.rb
index 0c9b2ff0d2..7c246326ca 100644
--- a/lib/ipaddr.rb
+++ b/lib/ipaddr.rb
@@ -483,7 +483,7 @@ class IPAddr
     if prefixlen
       mask!(prefixlen)
     else
-      @mask_addr = (family == Socket::AF_INET) ? IN4MASK : IN6MASK
+      @mask_addr = (@family == Socket::AF_INET) ? IN4MASK : IN6MASK
     end
   end