diff --git a/src/tracker/index.js b/src/tracker/index.js
index ace1d7c2..1c2fcc20 100644
--- a/src/tracker/index.js
+++ b/src/tracker/index.js
@@ -33,6 +33,10 @@
   /* Helper functions */
 
   const encode = str => {
+    if (!str) {
+      return undefined;
+    }
+
     try {
       const result = decodeURI(str);