Creating columns of typ SET fails to set default value

When writing a migration class for a table I wanted to add a new column of the SET type. I've set the notnull option and a default value, but Doctrine fails to generate the correct SQL.

Migration function:
public function up()

MySQL error (contains the generated SQL):
Error #1 - SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NOT NULL' at line 1. Failing Query: "ALTER TABLE my_table ADD new_field SET('value_a', 'value_b', 'value_c') DEFAULT NOT NULL"

After a bit of debugging I've found the problem, Doctrine_Formatter::quote() doesn't know how to handle set. Simply adding 'set' to the switch right below 'enum' will make it work as it should.

— lib/Doctrine/Formatter.php
+++ lib/Doctrine/Formatter.php
@@ -186,6 +186,7 @@ class Doctrine_Formatter extends Doctrine_Connection_Module
case 'blob':
case 'clob':
case 'enum':
+ case 'set':
case 'boolean':
return "'" . str_replace("'","''",$input) . "'";
}