Add entry to CHANGELOG

CHANGELOG.md

@@ -5,6 +5,15 @@ Documentation of all notable changes to the **EVMC** project.
 The format is based on [Keep a Changelog],
 and this project adheres to [Semantic Versioning].
 
+## [6.3.1] - unreleased
+
+### Fixed
+
+- In C++ API the `get_balance()` method now returns expected `evmc::uint256be` 
+  instead of `evmc_uint256be`.
+  [[#403](https://github.com/ethereum/evmc/pull/403)]
+
+
 ## [6.3.0] - 2019-08-12
 
 ### Added
@@ -319,6 +328,7 @@ and this project adheres to [Semantic Versioning].
   [[#52](https://github.com/ethereum/evmc/pull/52)]
 
 
+[6.3.1]: https://github.com/ethereum/evmc/compare/v6.3.0...release/6.3
 [6.3.0]: https://github.com/ethereum/evmc/releases/tag/v6.3.0
 [6.2.2]: https://github.com/ethereum/evmc/releases/tag/v6.2.2
 [6.2.1]: https://github.com/ethereum/evmc/releases/tag/v6.2.1