[NTG-context] \writebetweenllst not working for frontmatter material?

hello list, I want a TOC in which there is a blank line AFTER the first chapter in the TOC and BEFORE the last chapter in the TOC. (other chapter entries in the TOC don't have blank lines between them). I can achieve this with: \writebetweenlist[chapter]{\blank} but unfortutaly for chapter in frontmatter the above method does not produce a blank line in the TOC. Anyone has a clue as why not? Greetings, Rob