@@ -4,6 +4,7 @@ import (

 	"fmt"

 	"net"

 	"os"

+	"runtime"

 	"strings"

 	fopts "github.com/docker/docker/opts"

@@ -45,6 +46,12 @@ func ValidateEnv(val string) (string, error) {

 func doesEnvExist(name string) bool {

 	for _, entry := range os.Environ() {

 		parts := strings.SplitN(entry, "=", 2)

+		if runtime.GOOS == "windows" {

+			// Environment variable are case-insensitive on Windows. PaTh, path and PATH are equivalent.

+			if strings.EqualFold(parts[0], name) {

+				return true

+			}

+		}

 		if parts[0] == name {

 			return true

 		}

@@ -3,6 +3,7 @@ package opts

 import (

 	"fmt"

 	"os"

+	"runtime"

 	"strings"

 	"testing"

 )

@@ -50,6 +51,10 @@ func TestValidateEnv(t *testing.T) {

 		"  some space before": "  some space before",

 		"some space after  ":  "some space after  ",

 	}

+	// Environment variables are case in-sensitive on Windows

+	if runtime.GOOS == "windows" {

+		valids["PaTh"] = fmt.Sprintf("PaTh=%v", os.Getenv("PATH"))

+	}

 	for value, expected := range valids {

 		actual, err := ValidateEnv(value)

 		if err != nil {