diff --git a/ChangeLog b/ChangeLog
index 9cc3045b39..bd0ac0531b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Mon Jul  1 20:22:00 2013  Kenta Murata  <mrkn@cookpad.com>
+
+	* ext/bigdecimal/bigdecimal.h (RB_UNUSED_VAR, UNREACHABLE):
+	  import macros from ruby.h for 1.9.3.
+	  [Bug #8588] [ruby-core:55730]
+
+	* ext/bigdecimal/bigdecimal.gemspec: Bump version to 1.2.1.
+
 Mon Jul  1 20:03:39 2013  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/ipsocket.c (init_inetsock_internal): Use an address
diff --git a/ext/bigdecimal/bigdecimal.gemspec b/ext/bigdecimal/bigdecimal.gemspec
index d5622fb97d..bb85526f62 100644
--- a/ext/bigdecimal/bigdecimal.gemspec
+++ b/ext/bigdecimal/bigdecimal.gemspec
@@ -1,5 +1,5 @@
 # -*- ruby -*-
-_VERSION = "1.2.0"
+_VERSION = "1.2.1"
 
 Gem::Specification.new do |s|
   s.name = "bigdecimal"
diff --git a/ext/bigdecimal/bigdecimal.h b/ext/bigdecimal/bigdecimal.h
index a53ad47e81..e7a8bccee7 100644
--- a/ext/bigdecimal/bigdecimal.h
+++ b/ext/bigdecimal/bigdecimal.h
@@ -19,6 +19,18 @@
 #include "ruby/ruby.h"
 #include <float.h>
 
+#ifndef RB_UNUSED_VAR
+# ifdef __GNUC__
+#  define RB_UNUSED_VAR(x) x __attribute__ ((unused))
+# else
+#  define RB_UNUSED_VAR(x) x
+# endif
+#endif
+
+#ifndef UNREACHABLE
+# define UNREACHABLE		/* unreachable */
+#endif
+
 #undef BDIGIT
 #undef SIZEOF_BDIGITS
 #undef BDIGIT_DBL