diff --git a/lib/stringMsg.js b/lib/stringMsg.js
index 6ae357a..80a5a5c 100644
--- a/lib/stringMsg.js
+++ b/lib/stringMsg.js
@@ -19,13 +19,17 @@ const {
  * @param  {Object} [rest={}] Anything else to be added like len, timestamp, direction.
  * @return {Object}           All canId fields with format and data props added.
  */
-function buildMsg(canIdInfo, format, data, rest = {}) {
-  return {
-    ...canIdInfo,
+function buildMsg(_canIdInfo, format, data, rest = {}) {
+  const canIdInfo = Object.assign({}, _canIdInfo, {
     format,
-    data,
-    ...rest,
+    data
+  })
+  for (const property in rest) {
+    if (canIdInfo[property] === undefined) {
+      canIdInfo[property] = rest[property]
+    }
   }
+  return canIdInfo
 }
 function buildErrMsg(msg, input) {
   if (input && isString(input)) return `${msg} - ${input}`