diff --git a/fileinfo_go1.15.go b/fileinfo_go1.15.go
deleted file mode 100644
index c0708ea..0000000
--- a/fileinfo_go1.15.go
+++ /dev/null
@@ -1,17 +0,0 @@
-//go:build !go1.16
-// +build !go1.16
-
-package copy
-
-import "os"
-
-// This is a cloned definition of os.FileInfo (go1.15) or fs.FileInfo (go1.16~)
-// A FileInfo describes a file and is returned by Stat.
-type fileInfo interface {
-	// Name() string       // base name of the file
-	// Size() int64        // length in bytes for regular files; system-dependent for others
-	Mode() os.FileMode // file mode bits
-	// ModTime() time.Time // modification time
-	IsDir() bool      // abbreviation for Mode().IsDir()
-	Sys() interface{} // underlying data source (can return nil)
-}
diff --git a/fileinfo_go1.16.go b/fileinfo_go1.16.go
deleted file mode 100644
index 01b3fd2..0000000
--- a/fileinfo_go1.16.go
+++ /dev/null
@@ -1,17 +0,0 @@
-//go:build go1.16
-// +build go1.16
-
-package copy
-
-import "io/fs"
-
-// This is a cloned definition of os.FileInfo (go1.15) or fs.FileInfo (go1.16~)
-// A FileInfo describes a file and is returned by Stat.
-type fileInfo interface {
-	// Name() string       // base name of the file
-	// Size() int64        // length in bytes for regular files; system-dependent for others
-	Mode() fs.FileMode // file mode bits
-	// ModTime() time.Time // modification time
-	IsDir() bool      // abbreviation for Mode().IsDir()
-	Sys() interface{} // underlying data source (can return nil)
-}
diff --git a/patherror_go1.15_test.go b/patherror_go1.15_test.go
deleted file mode 100644
index 2566f3b..0000000
--- a/patherror_go1.15_test.go
+++ /dev/null
@@ -1,41 +0,0 @@
-//go:build !go1.16
-// +build !go1.16
-
-package copy
-
-import (
-	"os"
-	"path/filepath"
-	"runtime"
-	"testing"
-
-	. "github.com/otiai10/mint"
-)
-
-func TestCopy_PathError(t *testing.T) {
-
-	When(t, "too long name is given", func(t *testing.T) {
-		dest := "foobar"
-		for i := 0; i < 8; i++ {
-			dest = dest + dest
-		}
-		err := Copy("test/data/case00", filepath.Join("test/data/case00", dest))
-		Expect(t, err).Not().ToBe(nil)
-		Expect(t, err).TypeOf("*os.PathError")
-	})
-
-	When(t, "try to create not permitted location", func(t *testing.T) {
-		if runtime.GOOS == "windows" || runtime.GOOS == "freebsd" || os.Getenv("TESTCASE") != "" {
-			t.Skipf("FIXME: error IS nil here in Windows and FreeBSD")
-		}
-		err := Copy("test/data/case00", "/case00")
-		Expect(t, err).Not().ToBe(nil)
-		Expect(t, err).TypeOf("*os.PathError")
-	})
-
-	When(t, "try to create a directory on existing file name", func(t *testing.T) {
-		err := Copy("test/data/case02", "test/data.copy/case00/README.md")
-		Expect(t, err).Not().ToBe(nil)
-		Expect(t, err).TypeOf("*os.PathError")
-	})
-}
diff --git a/patherror_go1.16_test.go b/patherror_test.go
similarity index 96%
rename from patherror_go1.16_test.go
rename to patherror_test.go
index 2852e6c..40c03f6 100644
--- a/patherror_go1.16_test.go
+++ b/patherror_test.go
@@ -1,6 +1,3 @@
-//go:build go1.16
-// +build go1.16
-
 package copy
 
 import (
diff --git a/permission_control.go b/permission_control.go
index 97ae12d..cb4777c 100644
--- a/permission_control.go
+++ b/permission_control.go
@@ -1,6 +1,7 @@
 package copy
 
 import (
+	"io/fs"
 	"os"
 )
 
@@ -11,11 +12,11 @@ const (
 	tmpPermissionForDirectory = os.FileMode(0755)
 )
 
-type PermissionControlFunc func(srcinfo fileInfo, dest string) (chmodfunc func(*error), err error)
+type PermissionControlFunc func(srcinfo fs.FileInfo, dest string) (chmodfunc func(*error), err error)
 
 var (
 	AddPermission = func(perm os.FileMode) PermissionControlFunc {
-		return func(srcinfo fileInfo, dest string) (func(*error), error) {
+		return func(srcinfo fs.FileInfo, dest string) (func(*error), error) {
 			orig := srcinfo.Mode()
 			if srcinfo.IsDir() {
 				if err := os.MkdirAll(dest, tmpPermissionForDirectory); err != nil {
@@ -28,7 +29,7 @@ var (
 		}
 	}
 	PerservePermission PermissionControlFunc = AddPermission(0)
-	DoNothing          PermissionControlFunc = func(srcinfo fileInfo, dest string) (func(*error), error) {
+	DoNothing          PermissionControlFunc = func(srcinfo fs.FileInfo, dest string) (func(*error), error) {
 		if srcinfo.IsDir() {
 			if err := os.MkdirAll(dest, srcinfo.Mode()); err != nil {
 				return func(*error) {}, err
diff --git a/preserve_owner.go b/preserve_owner.go
index 13ec4f5..ca71132 100644
--- a/preserve_owner.go
+++ b/preserve_owner.go
@@ -4,11 +4,12 @@
 package copy
 
 import (
+	"io/fs"
 	"os"
 	"syscall"
 )
 
-func preserveOwner(src, dest string, info fileInfo) (err error) {
+func preserveOwner(src, dest string, info fs.FileInfo) (err error) {
 	if info == nil {
 		if info, err = os.Stat(src); err != nil {
 			return err
diff --git a/preserve_owner_x.go b/preserve_owner_x.go
index 9d82574..d6a6148 100644
--- a/preserve_owner_x.go
+++ b/preserve_owner_x.go
@@ -3,6 +3,8 @@
 
 package copy
 
-func preserveOwner(src, dest string, info fileInfo) (err error) {
+import "io/fs"
+
+func preserveOwner(src, dest string, info fs.FileInfo) (err error) {
 	return nil
 }