Mysql enum default values not quoted

From http://forum.liquibase.org/topic/default-value-of-timestamp-and-set-enum-maybe-others-not-enclosed#49382000000945008

In Enum/Set (MySQL) columns, the default value in the corresponding statement (e.g. create table) does not enclose the strings, that are mapped by MySQL to integers correct.
Example:

CREATE TABLE test (
val ENUM('a','b') DEFAULT 'a' NOT NULL
);

will be translated into:

<createTable tableName="test">
<column defaultValue="a" name="val" type="ENUM('a','b')">
<constraints nullable="false"/>
</column>
</createTable>

which is interpreted by the migrate command as

CREATE TABLE test (
val ENUM('a','b') DEFAULT a NOT NULL
);

which s not valid because the strings are not enclosed.