diff --git a/lib/websocket.js b/lib/websocket.js
index ddb44aed5de406b61320725b565bd75a6e9946c1..5b40075e43b258ed7f84b0615cc2b5d0565a0b8f 100644
--- a/lib/websocket.js
+++ b/lib/websocket.js
@@ -74,4 +74,5 @@ Object.defineProperty(WebSocketProvider.prototype, "onmessage", {
     set: function(provider) { this.onMessage(provider); }
 });
 
-module.exports = WebSocketProvider;
+if (typeof(module) !== "undefined")
+    module.exports = WebSocketProvider;