diff --git a/pytorch_lightning/callbacks/device_stats_monitor.py b/pytorch_lightning/callbacks/device_stats_monitor.py
index 00fd79d0f7..7b181fe463 100644
--- a/pytorch_lightning/callbacks/device_stats_monitor.py
+++ b/pytorch_lightning/callbacks/device_stats_monitor.py
@@ -100,12 +100,7 @@ class DeviceStatsMonitor(Callback):
             logger.log_metrics(prefixed_device_stats, step=trainer.fit_loop.epoch_loop._batches_that_stepped)
 
     def on_train_batch_start(
-        self,
-        trainer: "pl.Trainer",
-        pl_module: "pl.LightningModule",
-        batch: Any,
-        batch_idx: int,
-        unused: Optional[int] = 0,
+        self, trainer: "pl.Trainer", pl_module: "pl.LightningModule", batch: Any, batch_idx: int
     ) -> None:
         self._get_and_log_device_stats(trainer, "on_train_batch_start")