diff --git a/ChangeLog b/ChangeLog
new file mode 100644
index 0000000..b5bc71e
--- /dev/null
+++ b/ChangeLog
@@ -0,0 +1,11 @@
+version 0.9.1
+
+	* implements the server-side locking mechanism.
+	* new command line option "-v" shows the version and copyrights.
+	* fixed bugs: #2
+
+version 0.9.0
+
+	* The first public release.
+	* implements memcached ASCII and binary protocols.
+	* implements master-slave replication.
diff --git a/src/constants.hpp b/src/constants.hpp
index 693ad25..6b45ed2 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -28,7 +28,7 @@ const int           MAX_WORKERS        = 64;
 const std::size_t   MAX_REQUEST_LENGTH = 30 << 20; // 30 MiB
 const int           MAX_SLAVES         = 5;
 
-const char          VERSION[] = "yrmcds version 0.9.0";
+const char          VERSION[] = "yrmcds version 0.9.1";
 
 } // namespace yrmcds