diff --git a/xcdat/temporal.py b/xcdat/temporal.py
index ecb373c4..9b27d7d3 100644
--- a/xcdat/temporal.py
+++ b/xcdat/temporal.py
@@ -1085,9 +1085,9 @@ def _drop_incomplete_djf(self, dataset: xr.Dataset) -> xr.Dataset:
             ds[self.dim].dt.year.values[-1],
         )
         incomplete_seasons = (
-            f"{start_year:04d}-01",
-            f"{start_year:04d}-02",
-            f"{end_year:04d}-12",
+            f"{int(start_year):04d}-01",
+            f"{int(start_year):04d}-02",
+            f"{int(end_year):04d}-12",
         )
 
         for year_month in incomplete_seasons: