diff --git a/ChangeLog b/ChangeLog
index eb3d89b1ed..168343b24c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Jun 24 17:04:39 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/io/wait/extconf.rb: check sys/socket.h for cygwin.
+
 Tue Jun 24 16:51:51 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* io.c (io_reopen): remove cygwin handling because it seems to be for
diff --git a/ext/io/wait/extconf.rb b/ext/io/wait/extconf.rb
index e8181d25f5..1a0edbd846 100644
--- a/ext/io/wait/extconf.rb
+++ b/ext/io/wait/extconf.rb
@@ -2,7 +2,7 @@ require 'mkmf'
 target = "io/wait"
 
 unless macro_defined?("DOSISH", "#include <ruby.h>")
-  fionread = %w[sys/ioctl.h sys/filio.h].find do |h|
+  fionread = %w[sys/ioctl.h sys/filio.h sys/socket.h].find do |h|
     have_macro("FIONREAD", h)
   end
   if fionread