diff --git a/lib/cast/number.js b/lib/cast/number.js
index abc22f65cb9..18d2eebe6fd 100644
--- a/lib/cast/number.js
+++ b/lib/cast/number.js
@@ -29,7 +29,7 @@ module.exports = function castNumber(val) {
 
   assert.ok(!isNaN(val));
   if (val instanceof Number) {
-    return val;
+    return val.valueOf();
   }
   if (typeof val === 'number') {
     return val;
@@ -38,7 +38,7 @@ module.exports = function castNumber(val) {
     return Number(val.valueOf());
   }
   if (val.toString && !Array.isArray(val) && val.toString() == Number(val)) {
-    return new Number(val);
+    return Number(val);
   }
 
   assert.ok(false);