diff --git a/validate_yaml.py b/validate_yaml.py
index f656ea3..09ce218 100755
--- a/validate_yaml.py
+++ b/validate_yaml.py
@@ -56,7 +56,9 @@ def check_flights(airlines: set[str]) -> None:
         assert "trip" in booking
         assert all(flight["airline"] in airlines for flight in booking["flights"])
         flight_count += len(booking["flights"])
-        co2_flight_count += len([flight for flight in booking["flights"] if "co2_kg" in flight])
+        co2_flight_count += len(
+            [flight for flight in booking["flights"] if "co2_kg" in flight]
+        )
         check_currency(booking)
 
         if prev_first_depart:
@@ -65,8 +67,10 @@ def check_flights(airlines: set[str]) -> None:
             ), "Bookings are not in chronological order by first flight's departure."
         prev_first_depart = booking["flights"][0]["depart"]
 
-    print(f"{len(bookings)} flight bookings, {flight_count} flights, "
-          f"{co2_flight_count} with CO2 numbers")
+    print(
+        f"{len(bookings)} flight bookings, {flight_count} flights, "
+        f"{co2_flight_count} with CO2 numbers"
+    )
 
 
 def check_trains() -> None: