@@ -162,6 +162,12 @@ func (ts *tarSum) Read(buf []byte) (int, error) {

 			currentHeader, err := ts.tarR.Next()

 			if err != nil {

 				if err == io.EOF {

+					if err := ts.tarW.Close(); err != nil {

+						return 0, err

+					}

+					if _, err := io.Copy(ts.gz, ts.bufTar); err != nil {

+						return 0, err

+					}

 					if err := ts.gz.Close(); err != nil {

 						return 0, err

 					}

@@ -2,7 +2,10 @@ package tarsum

 import (

 	"bytes"

+	"compress/gzip"

 	"crypto/rand"

+	"crypto/sha256"

+	"encoding/hex"

 	"fmt"

 	"io"

 	"io/ioutil"

@@ -113,6 +116,77 @@ func sizedTar(opts sizedOptions) io.Reader {

 	return fh

 }

+func emptyTarSum(gzip bool) (TarSum, error) {

+	reader, writer := io.Pipe()

+	tarWriter := tar.NewWriter(writer)

+

+	// Immediately close tarWriter and write-end of the

+	// Pipe in a separate goroutine so we don't block.

+	go func() {

+		tarWriter.Close()

+		writer.Close()

+	}()

+

+	return NewTarSum(reader, !gzip, Version0)

+}

+

+// TestEmptyTar tests that tarsum does not fail to read an empty tar

+// and correctly returns the hex digest of an empty hash.

+func TestEmptyTar(t *testing.T) {

+	// Test without gzip.

+	ts, err := emptyTarSum(false)

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	zeroBlock := make([]byte, 1024)

+	buf := new(bytes.Buffer)

+

+	n, err := io.Copy(buf, ts)

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	if n != int64(len(zeroBlock)) || !bytes.Equal(buf.Bytes(), zeroBlock) {

+		t.Fatalf("tarSum did not write the correct number of zeroed bytes: %d", n)

+	}

+

+	expectedSum := ts.Version().String() + "+sha256:" + hex.EncodeToString(sha256.New().Sum(nil))

+	resultSum := ts.Sum(nil)

+

+	if resultSum != expectedSum {

+		t.Fatalf("expected [%s] but got [%s]", expectedSum, resultSum)

+	}

+

+	// Test with gzip.

+	ts, err = emptyTarSum(true)

+	if err != nil {

+		t.Fatal(err)

+	}

+	buf.Reset()

+

+	n, err = io.Copy(buf, ts)

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	bufgz := new(bytes.Buffer)

+	gz := gzip.NewWriter(bufgz)

+	n, err = io.Copy(gz, bytes.NewBuffer(zeroBlock))

+	gz.Close()

+	gzBytes := bufgz.Bytes()

+

+	if n != int64(len(zeroBlock)) || !bytes.Equal(buf.Bytes(), gzBytes) {

+		t.Fatalf("tarSum did not write the correct number of gzipped-zeroed bytes: %d", n)

+	}

+

+	resultSum = ts.Sum(nil)

+

+	if resultSum != expectedSum {

+		t.Fatalf("expected [%s] but got [%s]", expectedSum, resultSum)

+	}

+}

+

 func TestTarSums(t *testing.T) {

 	for _, layer := range testLayers {

 		var (