diff --git a/usr.sbin/makefs/cd9660.c b/usr.sbin/makefs/cd9660.c
index 0a1156de362..472831672d7 100644
--- a/usr.sbin/makefs/cd9660.c
+++ b/usr.sbin/makefs/cd9660.c
@@ -1070,7 +1070,7 @@ cd9660_rename_filename(cd9660node *iter, int num, int delete_chars)
 
 	tmp = malloc(ISO_FILENAME_MAXLENGTH_WITH_PADDING);
 
-	while (i < num) {
+	while (i < num && iter) {
 		powers = 1;
 		count = 0;
 		digits = 1;