--- 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)