@@ -75,13 +75,18 @@ func GetHTTPErrorStatusCode(err error) int {

 	return statusCode

 }

+func apiVersionSupportsJSONErrors(version string) bool {

+	const firstAPIVersionWithJSONErrors = "1.23"

+	return version == "" || versions.GreaterThan(version, firstAPIVersionWithJSONErrors)

+}

+

 // MakeErrorHandler makes an HTTP handler that decodes a Docker error and

 // returns it in the response.

 func MakeErrorHandler(err error) http.HandlerFunc {

 	return func(w http.ResponseWriter, r *http.Request) {

 		statusCode := GetHTTPErrorStatusCode(err)

 		vars := mux.Vars(r)

-		if vars["version"] == "" || versions.GreaterThan(vars["version"], "1.23") {

+		if apiVersionSupportsJSONErrors(vars["version"]) {

 			response := &types.ErrorResponse{

 				Message: err.Error(),

 			}

@@ -5,18 +5,11 @@ import (

 	"net/http"

 	"runtime"

+	"github.com/docker/docker/api/errors"

 	"github.com/docker/docker/api/types/versions"

 	"golang.org/x/net/context"

 )

-type badRequestError struct {

-	error

-}

-

-func (badRequestError) HTTPErrorStatusCode() int {

-	return http.StatusBadRequest

-}

-

 // VersionMiddleware is a middleware that

 // validates the client and server versions.

 type VersionMiddleware struct {

@@ -44,10 +37,10 @@ func (v VersionMiddleware) WrapHandler(handler func(ctx context.Context, w http.

 		}

 		if versions.GreaterThan(apiVersion, v.defaultVersion) {

-			return badRequestError{fmt.Errorf("client is newer than server (client API version: %s, server API version: %s)", apiVersion, v.defaultVersion)}

+			return errors.NewBadRequestError(fmt.Errorf("client is newer than server (client API version: %s, server API version: %s)", apiVersion, v.defaultVersion))

 		}

 		if versions.LessThan(apiVersion, v.minVersion) {

-			return badRequestError{fmt.Errorf("client version %s is too old. Minimum supported API version is %s, please upgrade your client to a newer version", apiVersion, v.minVersion)}

+			return errors.NewBadRequestError(fmt.Errorf("client version %s is too old. Minimum supported API version is %s, please upgrade your client to a newer version", apiVersion, v.minVersion))

 		}

 		header := fmt.Sprintf("Docker/%s (%s)", v.serverVersion, runtime.GOOS)