diff --git a/index.js b/index.js
index 685e119..c672dca 100644
--- a/index.js
+++ b/index.js
@@ -60,6 +60,7 @@ class SamPlugin {
                   + '(e.g. "--output ./sam-template.yml" or "-o ./sam-template.yml")',
                 required: true,
                 shortcut: 'o',
+                type: 'string',
               },
             },
           }
@@ -222,4 +223,4 @@ class SamPlugin {
   }
 }
 
-module.exports = SamPlugin;
\ No newline at end of file
+module.exports = SamPlugin;