diff --git a/cli/index.ts b/cli/index.ts
index 483fbd6c..5ecb7e65 100644
--- a/cli/index.ts
+++ b/cli/index.ts
@@ -79,7 +79,7 @@ yargs
       yargs.option('o', {
         describe: 'Output file',
         alias: 'output',
-        type: 'number',
+        type: 'string',
         default: 'redoc-static.html',
       });