diff --git a/lib/attribute.js b/lib/attribute.js
index 0d1668d..4881c3d 100644
--- a/lib/attribute.js
+++ b/lib/attribute.js
@@ -76,7 +76,7 @@ function Attribute(options) {
     };
   });
 
-  if (options.vals)
+  if (options.vals !== undefined)
     this.vals = options.vals;
 
 }