diff --git a/usr.sbin/bsdinstall/partedit/partedit.c b/usr.sbin/bsdinstall/partedit/partedit.c
--- a/usr.sbin/bsdinstall/partedit/partedit.c
+++ b/usr.sbin/bsdinstall/partedit/partedit.c
@@ -428,14 +428,17 @@
 		free(tobesorted);
 	}
 
-	if (getenv("PATH_FSTAB") != NULL)
-		fstab_path = getenv("PATH_FSTAB");
-	else
+	fstab_path = getenv("PATH_FSTAB");
+	if (fstab_path == NULL)
 		fstab_path = "/etc/fstab";
 	fstab = fopen(fstab_path, "w+");
 	if (fstab == NULL) {
-		sprintf(message, "Cannot open fstab file %s for writing (%s)\n",
-		    getenv("PATH_FSTAB"), strerror(errno));
+		error = snprintf(message, sizeof(message), "Cannot open fstab file %s"
+			" for writing (%s)\n", fstab_path, strerror(errno));
+		if (error < 0) {
+			snprintf(message, sizeof(message), "Cannot open fstab file for"
+				" writing (%s)\n", strerror(errno));
+		}
 		conf.title = "Error";
 		bsddialog_msgbox(&conf, message, 0, 0);
 		return (-1);