diff --git a/workflow/ttlcontroller/ttlcontroller.go b/workflow/ttlcontroller/ttlcontroller.go
index 91d2b992bd52..d5862127a321 100644
--- a/workflow/ttlcontroller/ttlcontroller.go
+++ b/workflow/ttlcontroller/ttlcontroller.go
@@ -130,7 +130,12 @@ func (c *Controller) processNextWorkItem() bool {
 
 // enqueueWF conditionally queues a workflow to the ttl queue if it is within the deletion period
 func (c *Controller) enqueueWF(obj interface{}) {
-	wf, err := util.FromUnstructured(obj.(*unstructured.Unstructured))
+	un, ok := obj.(*unstructured.Unstructured)
+	if !ok {
+		log.Warnf("'%v' is not an unstructured", obj)
+		return
+	}
+	wf, err := util.FromUnstructured(un)
 	if err != nil {
 		log.Warnf("Failed to unmarshal workflow %v object: %v", obj, err)
 		return