commit https://github.com/vim/vim/commit/3bece9fee9c02934d3e295b29d253e13d4ef26a7 Author: Bram Moolenaar <Bram@vim.org> Date: Mon Feb 15 20:39:46 2016 +0100 patch 7.4.1322 Problem: Crash when unletting the variable that holds the channel in a callback function. (Christian Robinson) Solution: Increase the reference count while invoking the callback.