@@ -5,6 +5,8 @@ import (

 	"io"

 	"os"

 	"path/filepath"

+	"runtime"

+	"strings"

 	"github.com/docker/docker/builder"

 	"github.com/docker/docker/pkg/pools"

@@ -56,7 +58,7 @@ func (c *lazyContext) Stat(path string) (string, builder.FileInfo, error) {

 		return "", nil, errors.WithStack(convertPathError(err, cleanPath))

 	}

-	relPath, err := filepath.Rel(c.root, fullPath)

+	relPath, err := rel(c.root, fullPath)

 	if err != nil {

 		return "", nil, errors.WithStack(convertPathError(err, cleanPath))

 	}

@@ -82,7 +84,7 @@ func (c *lazyContext) Walk(root string, walkFn builder.WalkFunc) error {

 		return err

 	}

 	return filepath.Walk(fullPath, func(fullPath string, fi os.FileInfo, err error) error {

-		relPath, err := filepath.Rel(c.root, fullPath)

+		relPath, err := rel(c.root, fullPath)

 		if err != nil {

 			return errors.WithStack(err)

 		}

@@ -147,3 +149,18 @@ func convertPathError(err error, cleanpath string) error {

 	}

 	return err

 }

+

+func rel(basepath, targpath string) (string, error) {

+	// filepath.Rel can't handle UUID paths in windows

+	if runtime.GOOS == "windows" {

+		pfx := basepath + `\`

+		if strings.HasPrefix(targpath, pfx) {

+			p := strings.TrimPrefix(targpath, pfx)

+			if p == "" {

+				p = "."

+			}

+			return p, nil

+		}

+	}

+	return filepath.Rel(basepath, targpath)

+}