diff --git a/bin/observable.ts b/bin/observable.ts
index 3232bbb08..a97aed8e7 100644
--- a/bin/observable.ts
+++ b/bin/observable.ts
@@ -187,7 +187,7 @@ try {
         allowPositionals: true
       });
       await import("../src/convert.js").then((convert) =>
-        convert.convert(positionals, {output: String(output), files: true})
+        convert.convert(positionals, {output: output!, files: true})
       );
       break;
     }