diff --git a/leap_year.py b/leap_year.py
index 475402f..fa50033 100644
--- a/leap_year.py
+++ b/leap_year.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 
-def is_leap_year(year):
+def is_leap_year(year: int):
     return year % 4 == 0 and year % 100 != 0 or year % 400 == 0
 
 if __name__ == "__main__":