diff --git a/src/apscheduler/triggers/cron/expressions.py b/src/apscheduler/triggers/cron/expressions.py
index a21af7b8..5443367f 100644
--- a/src/apscheduler/triggers/cron/expressions.py
+++ b/src/apscheduler/triggers/cron/expressions.py
@@ -262,9 +262,9 @@ def __init__(self, last_day):
 
     def get_next_value(self, date, field):
         currval = field.get_value(date)
-        nextval = monthrange(date.year, date.month)[1]-self.last_day
+        nextval = monthrange(date.year, date.month)[1] - self.last_day
 
         return nextval if currval <= nextval else None
 
     def __str__(self):
-        return f"last-{self.last_day}"
\ No newline at end of file
+        return f"last-{self.last_day}"
diff --git a/src/apscheduler/triggers/cron/fields.py b/src/apscheduler/triggers/cron/fields.py
index 543955cc..a777fa62 100644
--- a/src/apscheduler/triggers/cron/fields.py
+++ b/src/apscheduler/triggers/cron/fields.py
@@ -13,8 +13,8 @@
 from .expressions import (
     WEEKDAYS,
     AllExpression,
-    LastNDayOfMonthExpression,
     LastDayOfMonthExpression,
+    LastNDayOfMonthExpression,
     MonthRangeExpression,
     RangeExpression,
     WeekdayPositionExpression,
@@ -123,7 +123,12 @@ def get_value(self, dateval: datetime) -> int:
 
 
 class DayOfMonthField(
-    BaseField, extra_compilers=(WeekdayPositionExpression, LastNDayOfMonthExpression, LastDayOfMonthExpression)
+    BaseField,
+    extra_compilers=(
+        WeekdayPositionExpression,
+        LastNDayOfMonthExpression,
+        LastDayOfMonthExpression,
+    ),
 ):
     __slots__ = ()