diff --git a/pytorch_lightning/accelerators/ddp_accelerator.py b/pytorch_lightning/accelerators/ddp_accelerator.py
index 687b5c21874fb..4c2754f4049bd 100644
--- a/pytorch_lightning/accelerators/ddp_accelerator.py
+++ b/pytorch_lightning/accelerators/ddp_accelerator.py
@@ -39,7 +39,7 @@
 
 class DDPAccelerator(Accelerator):
 
-    def __init__(self, trainer, cluster_environment=None, ddp_plugin=None):
+    def __init__(self, trainer=None, cluster_environment=None, ddp_plugin=None):
         """
         Runs training using DDP strategy on a single machine (manually, not via cluster start)