diff --git a/lib/camel_case_keys.js b/lib/camel_case_keys.js
index 557e4fe4..55e04f3e 100644
--- a/lib/camel_case_keys.js
+++ b/lib/camel_case_keys.js
@@ -29,18 +29,17 @@ function camelCaseKeys(obj) {
   if (typeof obj !== 'object') throw new TypeError('obj must be an object!');
 
   const keys = Object.keys(obj);
+  const { length } = keys;
   const result = {};
 
-  for (let i = 0, len = keys.length; i < len; i++) {
-    const key = keys[i];
-    const value = obj[key];
-    const newKey = toCamelCase(key);
+  for (let i = 0; i < length; i++) {
+    const oldKey = keys[i];
+    const newKey = toCamelCase(oldKey);
 
-    if (newKey === key) {
-      result[key] = value;
-    } else {
-      result[newKey] = value;
-      Object.defineProperty(result, key, {
+    result[newKey] = obj[oldKey];
+
+    if (newKey !== oldKey) {
+      Object.defineProperty(result, oldKey, {
         get: getter(newKey),
         set: setter(newKey),
         configurable: true,