diff --git a/maths/segmented_sieve.py b/maths/segmented_sieve.py
index 0054b0595..35ed9702b 100644
--- a/maths/segmented_sieve.py
+++ b/maths/segmented_sieve.py
@@ -3,7 +3,7 @@
 import math
 
 
-def sieve(n):
+def sieve(n: int) -> list[int]:
     """Segmented Sieve."""
     in_prime = []
     start = 2