diff --git a/pytorch_lightning/callbacks/gradient_accumulation_scheduler.py b/pytorch_lightning/callbacks/gradient_accumulation_scheduler.py
index 97ea02961925d1..6122e07a90fac7 100644
--- a/pytorch_lightning/callbacks/gradient_accumulation_scheduler.py
+++ b/pytorch_lightning/callbacks/gradient_accumulation_scheduler.py
@@ -56,7 +56,9 @@ def __init__(self, scheduling: dict):
 
         minimal_epoch = min(scheduling.keys())
         if minimal_epoch < 0:
-            raise IndexError(f"Epochs indexing from 1, epoch {minimal_epoch} cannot be interpreted correct")
+            raise IndexError(
+                f"Epochs indexing from 1, epoch {minimal_epoch} cannot be interpreted correct"
+            )
         if minimal_epoch != 0:  # if user didnt define first epoch accumulation factor
             scheduling.update({0: 1})