diff --git a/js/persistentWorkers.js b/js/persistentWorkers.js
index 23349ec1a449f175a1fd98c4e52e1ac94e413a97..0cb772041f743ff316391dd323df08cbb37510d1 100644
--- a/js/persistentWorkers.js
+++ b/js/persistentWorkers.js
@@ -5,7 +5,7 @@ function persistentWorkers(numWorkers){
     //check compatibility
     if (!(typeof window.Worker === "function")){
         console.log("workers not supported");
-        return nil;
+        return null;
     }
 
     //local variables