@@ -3,7 +3,6 @@ package layer // import "github.com/docker/docker/layer"

 import (

 	"compress/gzip"

 	"encoding/json"

-	"errors"

 	"fmt"

 	"io"

 	"io/ioutil"

@@ -16,6 +15,7 @@ import (

 	"github.com/docker/distribution"

 	"github.com/docker/docker/pkg/ioutils"

 	"github.com/opencontainers/go-digest"

+	"github.com/pkg/errors"

 	"github.com/sirupsen/logrus"

 )

@@ -194,8 +194,8 @@ func (fms *fileMetadataStore) GetCacheID(layer ChainID) (string, error) {

 	}

 	content := strings.TrimSpace(string(contentBytes))

-	if !stringIDRegexp.MatchString(content) {

-		return "", errors.New("invalid cache id value")

+	if content == "" {

+		return "", errors.Errorf("invalid cache id value")

 	}

 	return content, nil