diff --git a/src/vim9.h b/src/vim9.h
index ed5f676..60c54d9 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -90,7 +90,9 @@
     ISN_PUSHCHANNEL,	// push NULL channel
     ISN_PUSHJOB,	// push NULL job
     ISN_NEWLIST,	// push list from stack items, size is isn_arg.number
+			// -1 for null_list
     ISN_NEWDICT,	// push dict from stack items, size is isn_arg.number
+			// -1 for null_dict
     ISN_NEWPARTIAL,	// push NULL partial
 
     ISN_AUTOLOAD,	// get item from autoload import, function or variable