diff --git a/pytorch_lightning/models/trainer.py b/pytorch_lightning/models/trainer.py
index 0e741dd624..e4de4f519d 100644
--- a/pytorch_lightning/models/trainer.py
+++ b/pytorch_lightning/models/trainer.py
@@ -304,7 +304,7 @@ class Trainer(TrainerIO):
         if self.on_gpu:
             rank = 0
             self.experiment = self.experiment.get_meta_copy()
-            mp.spawn(self.dp_train, nprocs=len(self.data_parallel_device_ids), args=(model))
+            mp.spawn(self.dp_train, nprocs=len(self.data_parallel_device_ids), args=(model, ))
         else:
             self.__run_pretrain_routine(model)