commit https://github.com/vim/vim/commit/7707344ddec9069b495b2a5ed41f2104466fc88b Author: Bram Moolenaar <Bram@vim.org> Date: Sat Feb 13 23:23:53 2016 +0100 patch 7.4.1315 Problem: Using a channel handle does not allow for freeing it when unused. Solution: Add the Channel variable type.

--- a/src/json.c
+++ b/src/json.c
@@ -183,6 +183,7 @@ json_encode_item(garray_T *gap, typval_T
 
 	case VAR_FUNC:
 	case VAR_JOB:
+	case VAR_CHANNEL:
 	    /* no JSON equivalent TODO: better error */
 	    EMSG(_(e_invarg));
 	    return FAIL;