diff --git a/js/tools/build/ndn-js-uncomp.js b/js/tools/build/ndn-js-uncomp.js
index 31c3998..b947a5c 100644
--- a/js/tools/build/ndn-js-uncomp.js
+++ b/js/tools/build/ndn-js-uncomp.js
@@ -69,6 +69,9 @@
  */
 
 var WebSocketTransport = function WebSocketTransport() {    
+    if (!WebSocket)
+        throw new Error("WebSocket support is not available on this platform.");
+    
 	this.ws = null;
     this.connectedHost = null; // Read by NDN.
     this.connectedPort = null; // Read by NDN.