--- a/taskcluster/taskgraph/transforms/task.py
+++ b/taskcluster/taskgraph/transforms/task.py
@@ -1042,17 +1042,17 @@ def build_balrog_payload(config, task, t
                 'partial_versions': release_config.get('partial_versions', ""),
                 'platforms': worker['platforms'],
                 'rules_to_update': worker['rules-to-update'],
                 'require_mirrors': worker['require-mirrors'],
             })
         else:  # schedule / ship
             task_def['payload'].update({
                 'publish_rules': worker['publish-rules'],
-                'release_eta': worker.get('release-eta', config.params.get('release_eta', '')),
+                'release_eta': worker.get('release-eta', config.params.get('release_eta')) or '',
             })
 
 
 @payload_builder('bouncer-aliases')
 def build_bouncer_aliases_payload(config, task, task_def):
     worker = task['worker']
 
     task_def['payload'] = {