diff --git a/src/worker/index.js b/src/worker/index.js
index 9923ffd..7f0723c 100644
--- a/src/worker/index.js
+++ b/src/worker/index.js
@@ -40,7 +40,7 @@ function WorkerIndex(options){
         factory = factory.toString();
     }
 
-    const is_node_js = self["exports"];
+    const is_node_js = typeof window === "undefined" && self["exports"];
     const _self = this;
 
     this.worker = create(factory, is_node_js, options["worker"]);