Fixes argument errors with fallback chords. Thanks to xoro

celery/backends/base.py

@@ -162,7 +162,7 @@ class BaseBackend(object):
     def on_chord_part_return(self, task):
         pass
 
-    def on_chord_apply(self, setid, body, **kwargs):
+    def on_chord_apply(self, setid, body, *args, **kwargs):
         from celery.registry import tasks
         tasks["celery.chord_unlock"].apply_async((setid, body, ), kwargs,
                                                  countdown=1)

celery/task/chords.py

@@ -29,7 +29,8 @@ class Chord(current_app.Task):
             task.options.update(task_id=uuid, chord=body)
             r.append(current_app.AsyncResult(uuid))
         current_app.TaskSetResult(setid, r).save()
-        self.backend.on_chord_apply(setid, body, interval, max_retries)
+        self.backend.on_chord_apply(setid, body, interval,
+                                    max_retries=max_retries)
         return set.apply_async(taskset_id=setid)