diff --git a/ChangeLog b/ChangeLog
index fa4aae13c0..f5d1b5a2e3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Nov 17 13:43:46 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/socket/lib/socket.rb: UNIXSocket is not always exists.  fixes
+	  install error on Windows, introduced at r52601.
+
 Tue Nov 17 11:27:23 2015  Eric Wong  <e@80x24.org>
 
 	* ext/socket/lib/socket.rb (Socket#recvfrom_nonblock):
diff --git a/ext/socket/lib/socket.rb b/ext/socket/lib/socket.rb
index eaec14f933..df526d73c6 100644
--- a/ext/socket/lib/socket.rb
+++ b/ext/socket/lib/socket.rb
@@ -1347,4 +1347,4 @@ class UNIXServer < UNIXSocket
   def accept_nonblock(exception: true)
     __accept_nonblock(exception)
   end
-end
+end if defined?(UNIXSocket)