diff --git a/kobo/worker/task.py b/kobo/worker/task.py
index 891b08ff..8be52220 100644
--- a/kobo/worker/task.py
+++ b/kobo/worker/task.py
@@ -32,7 +32,8 @@ def __init__(self, hub, conf, task_id, args):
         self._task_info = self.hub.worker.get_task(self.task_id)
         self._task_manager = None  # created by taskmanager (only for foreground tasks)
         self._args = args
-        self._subtask_list = []
+        self._finished_subtasks = set()
+        self._running_subtask_list = []
         self.result = ""
 
     @property
@@ -71,7 +72,7 @@ def args(self):
     @property
     def subtask_list(self):
         # deepcopy to prevent modification
-        return copy.deepcopy(self._subtask_list)
+        return copy.deepcopy(self._running_subtask_list)
 
     def run(self):
         """Run the task."""
@@ -95,7 +96,7 @@ def spawn_subtask(self, method, args, label="", priority = None):
             raise RuntimeError("Foreground tasks can't spawn subtasks.")
 
         subtask_id = self.hub.worker.create_subtask(label, method, args, self.task_id, priority)
-        self._subtask_list.append(subtask_id)
+        self._running_subtask_list.append(subtask_id)
         return subtask_id
 
     def wait(self, subtasks=None):
@@ -126,13 +127,19 @@ def wait(self, subtasks=None):
             signal.pause()
             # wake up on signal to check the status
 
+        # do not await subtasks that were already processed in previous wait calls
+        finished = [x for x in finished if x not in self._finished_subtasks]
+
         # remove finished subtasks from the list, check results
         fail = False
         for i in finished:
             state = self.hub.worker.get_task(i)
             if state['state'] != TASK_STATES['CLOSED']:
                 fail = True
-            self._subtask_list.remove(i)
+            self._running_subtask_list.remove(i)
+
+        # mark finished subtasks as processed
+        self._finished_subtasks.update(finished)
 
         if fail:
             print("Failing because of at least one subtask hasn't closed properly.")
diff --git a/tests/test_taskbase.py b/tests/test_taskbase.py
index 8a04fde6..266780a5 100644
--- a/tests/test_taskbase.py
+++ b/tests/test_taskbase.py
@@ -93,15 +93,15 @@ def test_subtask_list(self):
         args = []
 
         t = TaskBase(hub, conf, task_id, args)
-        self.assertEqual(len(t._subtask_list), 0)
+        self.assertEqual(len(t._running_subtask_list), 0)
 
         # access directly
-        t._subtask_list.append({'id': 1})
-        self.assertEqual(len(t._subtask_list), 1)
+        t._running_subtask_list.append({'id': 1})
+        self.assertEqual(len(t._running_subtask_list), 1)
 
         # copy to prevent modification
         t.subtask_list.append({'id': 2})
-        self.assertEqual(len(t._subtask_list), 1)
+        self.assertEqual(len(t._running_subtask_list), 1)
 
     def test_run(self):
         task_info = {'id': 100}