diff --git a/scripts/copy-res.ts b/scripts/copy-res.ts
index a13436b..fd5aa60 100755
--- a/scripts/copy-res.ts
+++ b/scripts/copy-res.ts
@@ -12,9 +12,9 @@ const argv = parseArgs(process.argv.slice(2), {});
 const watch = argv.w;
 const verbose = argv.v;
 
-function errCheck(err?: Error): void {
+function errCheck(err: unknown): void {
     if (err) {
-        console.error(err.message);
+        console.error(err instanceof Error ? err.message : err);
         process.exit(1);
     }
 }