diff --git a/lib/soap.js b/lib/soap.js
index 5e6b1f9..a6c8441 100644
--- a/lib/soap.js
+++ b/lib/soap.js
@@ -463,7 +463,9 @@ function request(httpRequest, cwmpVersion, warn) {
     }
   }
 
-  rpc.id = xml.get("/soap-env:Envelope/soap-env:Header/cwmp:ID", NAMESPACES[rpc.cwmpVersion]).text();
+  let idElement = xml.get("/soap-env:Envelope/soap-env:Header/cwmp:ID", NAMESPACES[rpc.cwmpVersion]);
+  if (idElement)
+    rpc.id = idElement.text();
 
   if (methodElement && !(XML_IGNORE_NAMESPACE && methodElement.name() === "Fault")) {
     switch (methodElement.name()) {