diff --git a/lib/api/middlewares/pubsub-metrics.js b/lib/api/middlewares/pubsub-metrics.js
index 7ccdb39c..c0d75552 100644
--- a/lib/api/middlewares/pubsub-metrics.js
+++ b/lib/api/middlewares/pubsub-metrics.js
@@ -45,6 +45,10 @@ function getEventData (req, res) {
 }
 
 function normalizedField (field) {
+    if (!field) {
+        return undefined;
+    }
+    
     return field.toString().trim().substr(0, MAX_LENGTH);
 }