MySQL diff - modify index key

mysql> create database test1 default character set utf8;
Query OK, 1 row affected (0.00 sec)
mysql> create database test2 default character set utf8;
Query OK, 1 row affected (0.00 sec)

mysql> use test1
Database changed
mysql> create table a (id int(10), c int(10), v int(10), b int(10), key cvb (c,v,b));
Query OK, 0 rows affected (0.00 sec)

mysql> use test2
Database changed
mysql> create table a (id int(10), c int(10),  v int(10), b int(10), key cvb (v,b));
Query OK, 0 rows affected (0.00 sec)


Liquibase Version: 3.2.2

Create diffChangeLog:
root@080c21576872:/opt# ./liquibase --driver=com.mysql.jdbc.Driver --classpath=/usr/share/java/mysql-connector-java-5.1.10.jar --url="jdbc:mysql://localhost/test2" --username=root --password='' diffChangeLog --referenceUrl="jdbc:mysql://localhost/test1" --referenceUsername=root --referencePassword='' > diff.xml
Liquibase 'diffChangeLog' Successful

root@080c21576872:/opt# cat diff.xml
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog" xmlns:ext="http://www.liquibase.org/xml/ns/dbchangelog-ext" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.2.xsd http://www.liquibase.org/xml/ns/dbchangelog-ext http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-ext.xsd">
    <changeSet author="root (generated)" id="1414522888481-1">
        <createIndex indexName="cvb" tableName="a" unique="false">
            <column name="c"/>
            <column name="v"/>
            <column name="b"/>
        </createIndex>
    </changeSet>
    <changeSet author="root (generated)" id="1414522888481-2">
        <dropIndex indexName="cvb" tableName="a"/>
    </changeSet>
</databaseChangeLog>


Update test2:
root@080c21576872:/opt# ./liquibase --driver=com.mysql.jdbc.Driver --classpath=/usr/share/java/mysql-connector-java-5.1.10.jar --url="jdbc:mysql://localhost/test2" --username=root --password='' --changeLogFile=diff.xml update
Unexpected error running Liquibase: Error executing SQL CREATE INDEX cvb ON test2.a(c, v, b): Duplicate key name 'cvb'


The sequence of actions in the file is broken.
modify file diff.xml:
root@080c21576872:/opt# cat diff.xml
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog" xmlns:ext="http://www.liquibase.org/xml/ns/dbchangelog-ext" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.2.xsd http://www.liquibase.org/xml/ns/dbchangelog-ext http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-ext.xsd">
    <changeSet author="root (generated)" id="1414522888481-2">
        <dropIndex indexName="cvb" tableName="a"/>
    </changeSet>
    <changeSet author="root (generated)" id="1414522888481-1">
        <createIndex indexName="cvb" tableName="a" unique="false">
            <column name="c"/>
            <column name="v"/>
            <column name="b"/>
        </createIndex>
    </changeSet>
</databaseChangeLog>

root@080c21576872:/opt# ./liquibase --driver=com.mysql.jdbc.Driver --classpath=/usr/share/java/mysql-connector-java-5.1.10.jar --url="jdbc:mysql://localhost/test2" --username=root --password='' --changeLogFile=diff.xml update
Liquibase Update Successful