diff --git a/go.mod b/go.mod
index 85cea67..0b44ed3 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@ module git.yetaga.in/alazyreader/libyear
 
 go 1.25.1
 
-require golang.org/x/mod v0.39.0
+require golang.org/x/mod v0.40.0
diff --git a/go.sum b/go.sum
index e33ffa2..b4d25a8 100644
--- a/go.sum
+++ b/go.sum
@@ -22,3 +22,5 @@ golang.org/x/mod v0.38.0 h1:MECBjubtXD7yj4HrhIUcywNaGeNVUdfVnxmPajOk4yk=
 golang.org/x/mod v0.38.0/go.mod h1:V6Xz0pq8TQ3dGqVQ1FVHuelZpAL0uNhSkk9ogYP3c40=
 golang.org/x/mod v0.39.0 h1:UF5zwQdCRRUpHfyPwr7d4UrGiVeldIsogtzWVnczL74=
 golang.org/x/mod v0.39.0/go.mod h1:bvIbwjQ0HUFFf5AKukeeYQG4ZBUG9yxQbR9aEweIwYY=
+golang.org/x/mod v0.40.0 h1:hUv+3cXcdRHz08UmSiOob7sadHig73uo5bkXxQ/tvUs=
+golang.org/x/mod v0.40.0/go.mod h1:0/weTWkPWGBikyTWAX3dkjVztMmBA5hM0DH6BElSupE=