diff --git a/tasktiger/_internal.py b/tasktiger/_internal.py
index a5e1dacb..35204385 100644
--- a/tasktiger/_internal.py
+++ b/tasktiger/_internal.py
@@ -62,16 +62,15 @@ def gen_unique_id(queue, serialized_name, args, kwargs):
     Generates and returns a hex-encoded 256-bit ID for the given task name and
     args. Used to generate IDs for unique tasks or for task locks.
     """
+    data = {
+        'func': serialized_name,
+        'args': args,
+        'kwargs': kwargs,
+    }
+    if queue is not None:
+        data['queue'] = queue
     return hashlib.sha256(
-        json.dumps(
-            {
-                'queue': queue,
-                'func': serialized_name,
-                'args': args,
-                'kwargs': kwargs,
-            },
-            sort_keys=True,
-        ).encode('utf8')
+        json.dumps(data, sort_keys=True).encode('utf8')
     ).hexdigest()
 
 
diff --git a/tasktiger/worker.py b/tasktiger/worker.py
index beb4cdb7..66e12e89 100644
--- a/tasktiger/worker.py
+++ b/tasktiger/worker.py
@@ -857,13 +857,14 @@ def _execute_task_group(self, queue, tasks, all_task_ids, queue_lock):
                 if task.lock_key:
                     kwargs = task.kwargs
                     lock_id = gen_unique_id(
+                        None,
                         task.serialized_func,
                         None,
                         {key: kwargs.get(key) for key in task.lock_key},
                     )
                 else:
                     lock_id = gen_unique_id(
-                        task.serialized_func, task.args, task.kwargs
+                        None, task.serialized_func, task.args, task.kwargs
                     )
 
                 if lock_id not in lock_ids: