diff --git a/ChangeLog b/ChangeLog
index 545bc85868..852b71a1c8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue May 27 21:28:16 2014  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* ext/socket/ifaddr.c (ifaddr_inspect_flags): support IFF_SIMPLEX.
+
 Tue May 27 21:03:03 2014  Kouhei Sutou  <kou@cozmixng.org>
 
 	* test/rexml/: Use REXMLTests as wrapping module for REXML tests.
diff --git a/ext/socket/ifaddr.c b/ext/socket/ifaddr.c
index 4f0286c700..15395d7088 100644
--- a/ext/socket/ifaddr.c
+++ b/ext/socket/ifaddr.c
@@ -292,6 +292,9 @@ ifaddr_inspect_flags(ifa_flags_t flags, VALUE result)
 #ifdef IFF_ALLMULTI
     INSPECT_BIT(IFF_ALLMULTI, "ALLMULTI")
 #endif
+#ifdef IFF_SIMPLEX
+    INSPECT_BIT(IFF_SIMPLEX, "SIMPLEX")
+#endif
 #ifdef IFF_MASTER
     INSPECT_BIT(IFF_MASTER, "MASTER")
 #endif