Matrix plugin forwards subversion tag parameter value as null

I have a matrix job which has "List subversion tags and more" parameters. (i.e. variable name SELECT_BRANCH)

I try to use the variable in a shell script.

The builds fail because the variable contains the value null instead of the selected svn branch.

Executing printenv shows me:

SELECT_BRANCH=null

Note: Downgrade to Matrix Project Plugin version 1.6 fixes the issue.