Hello. You probably forgot to specify the readonly flag for $PPID. Micro patch attached.
--w vodz
--- var.c~ 2021-01-31 12:30:38.000000000 +0400
+++ var.c 2021-02-03 16:46:34.657412861 +0400
@@ -139,7 +139,7 @@
setvareq(defoptindvar, VTEXTFIXED);
fmtstr(ppid + 5, sizeof(ppid) - 5, "%ld", (long) getppid());
- setvareq(ppid, VTEXTFIXED);
+ setvareq(ppid, VTEXTFIXED|VREADONLY);
p = lookupvar("PWD");
if (p)
