diff --git a/api/client/cp.go b/api/client/cp.go
index a36212a79a..4876ae2cdc 100644
--- a/api/client/cp.go
+++ b/api/client/cp.go
@@ -15,6 +15,7 @@ import (
 	Cli "github.com/docker/docker/cli"
 	"github.com/docker/docker/pkg/archive"
 	flag "github.com/docker/docker/pkg/mflag"
+	"github.com/docker/docker/pkg/system"
 )
 
 type copyDirection int
@@ -101,7 +102,7 @@ func (cli *DockerCli) CmdCp(args ...string) error {
 // client, a `:` could be part of an absolute Windows path, in which case it
 // is immediately proceeded by a backslash.
 func splitCpArg(arg string) (container, path string) {
-	if filepath.IsAbs(arg) {
+	if system.IsAbs(arg) {
 		// Explicit local absolute path, e.g., `C:\foo` or `/foo`.
 		return "", arg
 	}
@@ -236,7 +237,7 @@ func (cli *DockerCli) copyToContainer(srcPath, dstContainer, dstPath string) (er
 	// If the destination is a symbolic link, we should evaluate it.
 	if err == nil && dstStat.Mode&os.ModeSymlink != 0 {
 		linkTarget := dstStat.LinkTarget
-		if !filepath.IsAbs(linkTarget) {
+		if !system.IsAbs(linkTarget) {
 			// Join with the parent directory.
 			dstParent, _ := archive.SplitPathDirEntry(dstPath)
 			linkTarget = filepath.Join(dstParent, linkTarget)
diff --git a/builder/dispatchers.go b/builder/dispatchers.go
index 00e85b9236..78e3f87229 100644
--- a/builder/dispatchers.go
+++ b/builder/dispatchers.go
@@ -10,7 +10,7 @@ package builder
 import (
 	"fmt"
 	"io/ioutil"
-	"path"
+	"os"
 	"path/filepath"
 	"regexp"
 	"runtime"
@@ -21,6 +21,7 @@ import (
 	flag "github.com/docker/docker/pkg/mflag"
 	"github.com/docker/docker/pkg/nat"
 	"github.com/docker/docker/pkg/stringutils"
+	"github.com/docker/docker/pkg/system"
 	"github.com/docker/docker/runconfig"
 )
 
@@ -272,39 +273,15 @@ func workdir(b *builder, args []string, attributes map[string]bool, original str
 		return err
 	}
 
-	// Note that workdir passed comes from the Dockerfile. Hence it is in
-	// Linux format using forward-slashes, even on Windows. However,
-	// b.Config.WorkingDir is in platform-specific notation (in other words
-	// on Windows will use `\`
-	workdir := args[0]
+	// This is from the Dockerfile and will not necessarily be in platform
+	// specific semantics, hence ensure it is converted.
+	workdir := filepath.FromSlash(args[0])
 
-	isAbs := false
-	if runtime.GOOS == "windows" {
-		// Alternate processing for Windows here is necessary as we can't call
-		// filepath.IsAbs(workDir) as that would verify Windows style paths,
-		// along with drive-letters (eg c:\pathto\file.txt). We (arguably
-		// correctly or not) check for both forward and back slashes as this
-		// is what the 1.4.2 GoLang implementation of IsAbs() does in the
-		// isSlash() function.
-		isAbs = workdir[0] == '\\' || workdir[0] == '/'
-	} else {
-		isAbs = filepath.IsAbs(workdir)
+	if !system.IsAbs(workdir) {
+		current := filepath.FromSlash(b.Config.WorkingDir)
+		workdir = filepath.Join(string(os.PathSeparator), current, workdir)
 	}
 
-	if !isAbs {
-		current := b.Config.WorkingDir
-		if runtime.GOOS == "windows" {
-			// Convert to Linux format before join
-			current = strings.Replace(current, "\\", "/", -1)
-		}
-		// Must use path.Join so works correctly on Windows, not filepath
-		workdir = path.Join("/", current, workdir)
-	}
-
-	// Convert to platform specific format
-	if runtime.GOOS == "windows" {
-		workdir = strings.Replace(workdir, "/", "\\", -1)
-	}
 	b.Config.WorkingDir = workdir
 
 	return b.commit("", b.Config.Cmd, fmt.Sprintf("WORKDIR %v", workdir))
diff --git a/builder/internals.go b/builder/internals.go
index e7ce1b450a..dbd661c28f 100644
--- a/builder/internals.go
+++ b/builder/internals.go
@@ -270,7 +270,7 @@ func calcCopyInfo(b *builder, cmdName string, cInfos *[]*copyInfo, origPath stri
 
 	// Twiddle the destPath when its a relative path - meaning, make it
 	// relative to the WORKINGDIR
-	if !filepath.IsAbs(destPath) {
+	if !system.IsAbs(destPath) {
 		hasSlash := strings.HasSuffix(destPath, string(os.PathSeparator))
 		destPath = filepath.Join(string(os.PathSeparator), filepath.FromSlash(b.Config.WorkingDir), destPath)
 
diff --git a/pkg/archive/copy.go b/pkg/archive/copy.go
index a7ed12c1b3..ecfd0a9c69 100644
--- a/pkg/archive/copy.go
+++ b/pkg/archive/copy.go
@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"github.com/Sirupsen/logrus"
+	"github.com/docker/docker/pkg/system"
 )
 
 // Errors used or returned by this file.
@@ -210,7 +211,7 @@ func CopyInfoDestinationPath(path string) (info CopyInfo, err error) {
 			return CopyInfo{}, err
 		}
 
-		if !filepath.IsAbs(linkTarget) {
+		if !system.IsAbs(linkTarget) {
 			// Join with the parent directory.
 			dstParent, _ := SplitPathDirEntry(path)
 			linkTarget = filepath.Join(dstParent, linkTarget)
diff --git a/pkg/symlink/fs.go b/pkg/symlink/fs.go
index ef12f06bae..d305500453 100644
--- a/pkg/symlink/fs.go
+++ b/pkg/symlink/fs.go
@@ -12,6 +12,8 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+
+	"github.com/docker/docker/pkg/system"
 )
 
 // FollowSymlinkInScope is a wrapper around evalSymlinksInScope that returns an
@@ -120,7 +122,7 @@ func evalSymlinksInScope(path, root string) (string, error) {
 		if err != nil {
 			return "", err
 		}
-		if filepath.IsAbs(dest) {
+		if system.IsAbs(dest) {
 			b.Reset()
 		}
 		path = dest + string(filepath.Separator) + path