diff --git a/examples/event-sources/mqtt.yaml b/examples/event-sources/mqtt.yaml
index 9623e62ee6..8a6fa89e17 100644
--- a/examples/event-sources/mqtt.yaml
+++ b/examples/event-sources/mqtt.yaml
@@ -13,7 +13,7 @@ spec:
       # source will be JSON
       jsonBody: true
       # client id
-      clientId: 2345
+      clientId: "2345"
       # optional backoff time for connection retries.
       # if not provided, default connection backoff time will be used.
       connectionBackoff:
@@ -30,7 +30,7 @@ spec:
 #      url: "tcp://mqtt.argo-events:1883"
 #      topic: "bar"
 #      jsonBody: true
-#      clientId: 2345
+#      clientId: "2345"
 #      tls:
 #        caCertSecret:
 #          name: my-secret