diff --git a/fs.go b/fs.go
index a9efccd..d86f9d8 100644
--- a/fs.go
+++ b/fs.go
@@ -164,6 +164,8 @@ type File interface {
 	// Name returns the name of the file as presented to Open.
 	Name() string
 	io.Writer
+	// TODO: Add io.WriterAt for v6  
+	// io.WriterAt
 	io.Reader
 	io.ReaderAt
 	io.Seeker
diff --git a/memfs/memory.go b/memfs/memory.go
index 2e17a3c..978fed1 100644
--- a/memfs/memory.go
+++ b/memfs/memory.go
@@ -272,6 +272,10 @@ func (f *file) Seek(offset int64, whence int) (int64, error) {
 }
 
 func (f *file) Write(p []byte) (int, error) {
+	return f.WriteAt(p, f.position)
+}
+
+func (f *file) WriteAt(p []byte, off int64) (int, error) {
 	if f.isClosed {
 		return 0, os.ErrClosed
 	}
@@ -280,8 +284,8 @@ func (f *file) Write(p []byte) (int, error) {
 		return 0, errors.New("write not supported")
 	}
 
-	n, err := f.content.WriteAt(p, f.position)
-	f.position += int64(n)
+	n, err := f.content.WriteAt(p, off)
+	f.position = off + int64(n)
 
 	return n, err
 }
diff --git a/test/mock.go b/test/mock.go
index 40cbbf5..f782b26 100644
--- a/test/mock.go
+++ b/test/mock.go
@@ -115,6 +115,10 @@ func (*FileMock) ReadAt(b []byte, off int64) (int, error) {
 	return 0, nil
 }
 
+func (*FileMock) WriteAt(b []byte, off int64) (int, error) {
+	return 0, nil
+}
+
 func (*FileMock) Seek(offset int64, whence int) (int64, error) {
 	return 0, nil
 }