diff --git a/cli/Csv2xlsxApp.php b/cli/Csv2xlsxApp.php
index 796536c..0ce7c43 100644
--- a/cli/Csv2xlsxApp.php
+++ b/cli/Csv2xlsxApp.php
@@ -2,15 +2,15 @@
 namespace cli;
 
 use nulib\app\cli\Application;
+use nulib\cv;
 use nulib\ext\tab\SsBuilder;
 use nulib\ext\tab\SsReader;
 use nulib\file;
 use nulib\os\path;
-use nulib\ValueException;
 
 class Csv2xlsxApp extends Application {
   function main() {
-    $input = ValueException::check_null($this->args[0] ?? null);
+    $input = cv::not_null($this->args[0] ?? null, "input");
     $inputname = path::filename($input);
     $output = path::ensure_ext($inputname, ".xlsx", ".csv");