diff --git a/CHANGELOG.md b/CHANGELOG.md
index ef79de76d..b9368a2c3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,9 +1,9 @@
 # Change Log
 
-## [v2.1.0](https://github.com/semuxproject/semux-core/tree/v2.1.0) (2019-09-xx)
+## [v2.1.x](https://github.com/semuxproject/semux-core/tree/v2.1.1) (2019-09-10)
 
-This release fixes several critical bugs of the v2 releases. All nodes should upgrade
-to this version ASAP.
+This release tries to fix several issues about the voting precompiled contracts. All nodes
+are required to upgrade.
 
 NOTE: A softfork `VOTING_PRECOMPILED_UPGRADE` is introduced.
 
@@ -14,44 +14,31 @@ NOTE: A softfork `VOTING_PRECOMPILED_UPGRADE` is introduced.
 - Fixed the local call bug (#257)
 
 **New features:**
-
-- CLI
-    - Added a database re-index tool (#262)
 - API
     - Bumped the version to `v2.4.0`
-    - Replaced `/syncing` with `/syncing-status` (#267)
-    - Replaced `/call` with `/local-call` (#267)
     - Deprecated `POST /transaction/raw` (#267)
     - Deprecated `POST /account` and `DELETE /account` (#267)
+    - Replaced `/call` with `/local-call` (#267)
+    - Added `/local-create` (#267)
     - Added `/broadcast-raw-transaction` (#267)
     - Added `/create-account` and `/delete-account` (#267)
-    - Added `/local-create` (#267)
     - Added `/account/code` and `/account/storage` (#266)
+- CLI
+    - Added a database re-index tool (#262)
 
-## [v2.0.0](https://github.com/semuxproject/semux-core/tree/v2.0.0) (2019-08-25)
 
-This release features the **virtual machine hardfork** and **HD wallet**.
+## [v2.0.x](https://github.com/semuxproject/semux-core/tree/v2.0.2) (2019-08-25)
 
-**Important notice**
+This release features the **virtual machine hardfork** and **HD wallet**.
 
-Please backup your wallet file, `wallet.data`, and do a full-sync with the network. Note that
-the configuration file has also been updated; suggest using the new one.
+NOTE: A softfork `VIRTUAL_MACHINE` is introduced.
 
 **Bug fixes:**
-
 - Fixed a capacity codec bug in P2P handshake (#214)
 - Fixed the invalid transaction results in database issue (#221)
 - Fixed various EVM integration issues (#182, #183, #184, #190, #209, #210, #224, #229)
 
-**Improvements:**
-
-- Updated docs (#156, #158, #193)
-- Reset the `testnet` with new keys (#175, #176)
-- Packed JVM images in releases (#225)
-- Added support for quotes in console dialog (#203)
-
 **New features:**
-
 - Consensus
     - Replaced the block size limit with a `20m` gas limit (#211, #213, #214)
 - Sync
@@ -68,27 +55,23 @@ the configuration file has also been updated; suggest using the new one.
 - GUI
     - Added support for quotes in console dialog (#203)
 
+**Enhancements:**
+- Updated docs (#156, #158, #193)
+- Reset the `testnet` with new keys (#175, #176)
+- Packed JVM images in releases (#225)
+- Added support for quotes in console dialog (#203)
+
 
-## [v1.4.0](https://github.com/semuxproject/semux-core/tree/v1.4.0) (2019-04-22)
+## [v1.4.x](https://github.com/semuxproject/semux-core/tree/v1.4.0) (2019-04-22)
 
 This release includes incremental improvements and bugfixes since last version. Major changes
 are the block rewards adjustment and virtual machine implementation (in place but **not activated**).
 
-**Bugfixes:**
+**Bug fixes:**
 - Fix the 2/3 BFT quorum size rounding error (#134, #142)
 - Start syncing when the number of connections is low (#130)
 
-**Improvements:**
-- Fast block validation using batch validation (#150)
-- Add `aarch64` native support (#89, #117)
-- Suggest use OpenJDK (#131)
-- Update error messages and descriptions (#81, #79, #94, #103)
-- Add empty password shortcut (#108)
-- Update dependent libraries (#79, #141)
-- Limit the number of validators on testnet (#123)
-
-**Features:**
-
+**New features:**
 - Consensus
     - Update the block reward function (#151)
 - VM
@@ -104,17 +87,27 @@ are the block rewards adjustment and virtual machine implementation (in place bu
 - P2P
     - Upgrade protocol to support light client (#146)
 
-## [v1.3.0](https://github.com/semuxproject/semux-core/tree/v1.3.0) (2018-08-05)
+**Enhancements:**
+- Fast block validation using batch validation (#150)
+- Add `aarch64` native support (#89, #117)
+- Suggest use OpenJDK (#131)
+- Update error messages and descriptions (#81, #79, #94, #103)
+- Add empty password shortcut (#108)
+- Update dependent libraries (#79, #141)
+- Limit the number of validators on testnet (#123)
+
+
+## [v1.3.x](https://github.com/semuxproject/semux-core/tree/v1.3.0) (2018-08-05)
 
 This release fix the validator timestamp issue and introduces fast syncing.
 
-**Bugfixes:**
+**Bug fixes:**
 - GUI
     - Fixed the sender address order issue
 - Tools
     - Fixed windows unicode directories 
 
-**Features and enhancements:**
+**Enhancements:**
 - Consensus
     - Changed the creation of block proposal timestamp
     - Introduced fast syncing
@@ -127,12 +120,11 @@ This release fix the validator timestamp issue and introduces fast syncing.
     - Added filter of duplicated transactions
 
 
-## [v1.2.0](https://github.com/semuxproject/semux-core/tree/v1.2.0) (2018-05-25)
+## [v1.2.x](https://github.com/semuxproject/semux-core/tree/v1.2.0) (2018-05-25)
 
 This release introduces Java 10 support plus a few API & documentation improvements for third-party service integration & light wallet implementation.
 
-**Fixed bugs:**
-
+**Bug fixes:**
 - Net
   - Fixed a memory leak caused by connection limiter
 - API 2.0.0
@@ -143,7 +135,6 @@ This release introduces Java 10 support plus a few API & documentation improveme
   - Fixed an issue that long aliases can break rendering
 
 **New features:**
-
 - Add Java 10 Support
 - Add API 2.1.0 based off API 2.0.0
   - Add `DELETE /account?address`
@@ -164,8 +155,7 @@ This release introduces Java 10 support plus a few API & documentation improveme
   - Provide safe ways for automatic wallet unlock to address an issue that `--password` CLI option exposes wallet password to process explorer
     - environment variable: `SEMUX_WALLET_PASSWORD`
 
-**Implemented enhancements:**
-
+**Enhancements:**
 - GUI
   - Rearrange sorting of delegate panel
     - Reflect internal validator positions within 200-block round
@@ -179,42 +169,18 @@ This release introduces Java 10 support plus a few API & documentation improveme
   - Improve API descriptions and validation patterns in swagger definition
   - Re-organize documentation
 
-## [v1.1.1](https://github.com/semuxproject/semux-core/tree/v1.1.1) (2018-04-22)
-[Full Changelog](https://github.com/semuxproject/semux-core/compare/v1.1.0...v1.1.1)
 
-**Fixed bugs:**
+## [v1.1.x](https://github.com/semuxproject/semux-core/tree/v1.1.0) (2018-04-15)
 
-- Fix a bug that database folders are wrongly named under Turkish Windows
+This release contains bug fixes and enhancements.
 
-**Implemented enhancements:**
-
-- Provide a consistent progressbar on OSX with Windows and Linux
-- Validate network name before startup
-- Optimize client version lookup
-- Change Windows Java download URL from java.com to oracle.com
-
-## [v1.1.0](https://github.com/semuxproject/semux-core/tree/v1.1.0) (2018-04-15)
-[Full Changelog](https://github.com/semuxproject/semux-core/compare/v1.0.1...v1.1.0)
-
-**UNIFORM_DISTRIBUTION Fork**
-
-`UNIFORM_DISTRIBUTION` fork is introduced in v1.1.0 to address issue
-
-Validators are strongly suggested to upgrade to v1.1.0 ASAP in order to participate in the activation of `UNIFORM_DISTRIBUTION` fork which will be activated as soon as there are 1500 out of past 2000 blocks signaling the fork.
-
-Please note your validator node will stop forging blocks if you are unable to install v1.1.0 in advance of fork activation.
-
-**Database Upgrade**
-
-v1.1.0 will automatically apply a local database upgrade which takes about 1 ~ 5 minutes during wallet startup. Please ensure that you have at least 3 GB of space left on your disk.
-
-**Fixed bugs:**
+A softfork `UNIFORM_DISTRIBUTION` is introduced.
 
+**Bug fixes:**
 - GUI: Fix model refresh delay
 - Consensus: Fix sync votes validation issue
 
-**Implemented enhancements:**
-
+**Enhancements:**
 - Core: Change default POSIX permissions of wallet.data and config files to 600
 - Docs: Basic introductions to Semux BFT consensus
 - GUI: Inform user when a new version of Semux Wallet has been posted
@@ -231,19 +197,12 @@ v1.1.0 will automatically apply a local database upgrade which takes about 1 ~ 5
 - GUI: Use BigDecimal instead of double for correctness
 - GUI: Refactor status bar
 
-**Testnet changes:**
-
-- Increase block size limit to 10 MB
 
-**Deprecations:**
+## [v1.0.x](https://github.com/semuxproject/semux-core/tree/v1.0.1) (2018-03-06)
 
-- API v1.0.1 is deprecated and planned to be removed in a future release
-
-## [v1.0.1](https://github.com/semuxproject/semux-core/tree/v1.0.1) (2018-03-06)
-[Full Changelog](https://github.com/semuxproject/semux-core/compare/v1.0.0...v1.0.1)
-
-**Fixed bugs:**
+This release contains bug fixes and enhancements.
 
+**Bug fixes:**
 - A validator node might stuck in sync process
     - Consensus: Don't sync when a validator is in FINALIZE state
     - Consensus: Fix unconditional wait of SemuxSync\#isRunning
@@ -254,8 +213,7 @@ v1.1.0 will automatically apply a local database upgrade which takes about 1 ~ 5
 - Net: Properly separate mainnet and testnet
 - CLI: Flush async loggers in `Launcher` class
 
-**Implemented enhancements:**
-
+**Enhancements:**
 - Add Java 9 Support
 - GUI: Support customized based unit and show full digits by default
 - GUI: Validate address alias length
diff --git a/pom.xml b/pom.xml
index abecc1298..f05de20df 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,7 +3,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>org.semux</groupId>
     <artifactId>semux</artifactId>
-    <version>2.1.0</version>
+    <version>2.1.1</version>
     <packaging>jar</packaging>
     <description>Semux is an experimental high-performance blockchain platform that powers decentralized application.</description>
 
diff --git a/src/main/java/org/semux/config/Constants.java b/src/main/java/org/semux/config/Constants.java
index fc98ddce9..92fe70ee5 100644
--- a/src/main/java/org/semux/config/Constants.java
+++ b/src/main/java/org/semux/config/Constants.java
@@ -14,11 +14,6 @@
 
 public class Constants {
 
-    /**
-     * JSON mime type string.
-     */
-    public static final String JSON_MIME = "application/json";
-
     /**
      * Default data directory.
      */
@@ -39,7 +34,7 @@ public class Constants {
     /**
      * Version of this client.
      */
-    public static final String CLIENT_VERSION = "2.1.0";
+    public static final String CLIENT_VERSION = "2.1.1";
 
     /**
      * Algorithm name for the 256-bit hash.