diff --git a/index.js b/index.js
index <HASH>..<HASH> 100644
--- a/index.js
+++ b/index.js
@@ -39,8 +39,8 @@ function _update(current, name, fn) {
     var lookupKey = key;
     key = lookupIndex(current, key);
     if (key === undefined) {
-      throw new Error(`no object found by ${lookupKey}. autocreate is not supported`);
-    } 
+      throw new Error('no object found by ' + lookupKey + '. autocreate is not supported');
+    }
   }
 
   if (current[key] === undefined) {
fix message interpolation when throwing lookup error

- accidental usage of ES6 interpolation causes problems
when processing code that expected to be ES5-compatible.
this commit replaces interpolation by string concatenation