diff --git a/cpp/ChangeLog b/cpp/ChangeLog
index 6d7f486d..a14807c8 100644
--- a/cpp/ChangeLog
+++ b/cpp/ChangeLog
@@ -1,4 +1,8 @@
 
+2011-04-24 version 0.5.6:
+
+  * #42 fixes double-free problem on msgpack_unpacker_release_zone
+
 2011-02-24 version 0.5.5:
 
   * eliminates dependency of winsock2.h header
diff --git a/cpp/configure.in b/cpp/configure.in
index f017b7cf..95635c3c 100644
--- a/cpp/configure.in
+++ b/cpp/configure.in
@@ -1,6 +1,6 @@
 AC_INIT(src/object.cpp)
 AC_CONFIG_AUX_DIR(ac)
-AM_INIT_AUTOMAKE(msgpack, 0.5.5)
+AM_INIT_AUTOMAKE(msgpack, 0.5.6)
 AC_CONFIG_HEADER(config.h)
 
 AC_SUBST(CFLAGS)