diff --git a/pytorch_lightning/trainer/training_loop.py b/pytorch_lightning/trainer/training_loop.py
index f80fb0d5b6f86..14408ec7695be 100644
--- a/pytorch_lightning/trainer/training_loop.py
+++ b/pytorch_lightning/trainer/training_loop.py
@@ -70,7 +70,6 @@ def on_trainer_init(
         self.trainer.batch_idx = 0
         self.trainer.num_training_batches = 0
         self.trainer.train_dataloader = None
-        self.automatic_optimization: bool = ...
 
         # If neither max_epochs or max_steps is set, then use existing default of max_epochs = 1000
         self.trainer.max_epochs = 1000 if (max_epochs is None and max_steps is None) else max_epochs