diff --git a/CHANGELOG.md b/CHANGELOG.md
index 63bed9bd..cd1c499c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,15 @@
+# 2021-08-01 version 4.0.0
+  * Fix and improve alignment logic (#962)
+  * Fix iovec name conflict (#953)
+  * Fix empty string print (#942)
+  * Fix buffer ptr size (#899)
+  * Fix UB. Check null pointer before using memcpy() (#890)
+  * Improve CI environment (#885, #899)
+
+## << breaking changes >>
+* Separate C part of the msgpack-c from C/C++ mixed msgpack-c (#876, #878)
+
+
 # 2020-06-05 version 3.3.0
   * Add json example for C (#870)
   * Add both header and body packing functions for C (#870)
diff --git a/README.md b/README.md
index 471dc87b..e8035965 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 `msgpack` for C
 ===================
 
-Version 3.3.0 [![Build Status](https://github.com/msgpack/msgpack-c/workflows/CI/badge.svg?branch=c_master)](https://github.com/msgpack/msgpack-c/actions) [![Build status](https://ci.appveyor.com/api/projects/status/8kstcgt79qj123mw/branch/c_master?svg=true)](https://ci.appveyor.com/project/redboltz/msgpack-c/branch/c_master)
+Version 4.0.0 [![Build Status](https://github.com/msgpack/msgpack-c/workflows/CI/badge.svg?branch=c_master)](https://github.com/msgpack/msgpack-c/actions) [![Build status](https://ci.appveyor.com/api/projects/status/8kstcgt79qj123mw/branch/c_master?svg=true)](https://ci.appveyor.com/project/redboltz/msgpack-c/branch/c_master)
 [![codecov](https://codecov.io/gh/msgpack/msgpack-c/branch/c_master/graph/badge.svg)](https://codecov.io/gh/msgpack/msgpack-c/branch/c_master)
 
 It's like JSON but smaller and faster.
diff --git a/appveyor.yml b/appveyor.yml
index 63e9da9c..ba1c221b 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,4 +1,4 @@
-version: 3.3.0.{build}
+version: 4.0.0.{build}
 
 branches:
   only:
diff --git a/include/msgpack/version_master.h b/include/msgpack/version_master.h
index 9db6023e..763c732c 100644
--- a/include/msgpack/version_master.h
+++ b/include/msgpack/version_master.h
@@ -1,3 +1,3 @@
-#define MSGPACK_VERSION_MAJOR    3
-#define MSGPACK_VERSION_MINOR    3
+#define MSGPACK_VERSION_MAJOR    4
+#define MSGPACK_VERSION_MINOR    0
 #define MSGPACK_VERSION_REVISION 0
diff --git a/makedist.sh b/makedist.sh
index d700a619..da7b039c 100755
--- a/makedist.sh
+++ b/makedist.sh
@@ -18,6 +18,7 @@ tar cf $filename $prefix/example
 tar --append --file=$filename $prefix/test
 tar --append --file=$filename $prefix/include
 tar --append --file=$filename $prefix/src
+tar --append --file=$filename $prefix/cmake
 
 tar --append --file=$filename $prefix/CMakeLists.txt
 tar --append --file=$filename $prefix/Files.cmake