diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f47d19f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.dccache
+
diff --git a/filter_test.go b/filter_test.go
index 8ac9185..b37b7e4 100644
--- a/filter_test.go
+++ b/filter_test.go
@@ -11,8 +11,9 @@ import (
 	"testing"
 	"time"
 
+	"log/slog"
+
 	"github.com/m-mizutani/masq"
-	"golang.org/x/exp/slog"
 )
 
 func newLogger(w io.Writer, f func(groups []string, a slog.Attr) slog.Attr) *slog.Logger {
diff --git a/go.mod b/go.mod
index 2e46bd0..8e792d1 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/m-mizutani/masq
 
-go 1.20
+go 1.21
 
 require (
 	github.com/m-mizutani/gt v0.0.0-20221229045033-48cc67569435
diff --git a/masq.go b/masq.go
index 5edb397..a1239b2 100644
--- a/masq.go
+++ b/masq.go
@@ -4,7 +4,7 @@ import (
 	"reflect"
 	"regexp"
 
-	"golang.org/x/exp/slog"
+	"log/slog"
 )
 
 const (
diff --git a/masq_test.go b/masq_test.go
index 673174e..ab3f201 100644
--- a/masq_test.go
+++ b/masq_test.go
@@ -3,8 +3,9 @@ package masq_test
 import (
 	"os"
 
+	"log/slog"
+
 	"github.com/m-mizutani/masq"
-	"golang.org/x/exp/slog"
 )
 
 type EmailAddr string