@@ -163,13 +163,17 @@ func newImageBuildOptions(ctx context.Context, r *http.Request) (*types.ImageBui

 }

 func parseVersion(s string) (types.BuilderVersion, error) {

-	if s == "" || s == string(types.BuilderV1) {

+	if s == "" {

 		return types.BuilderV1, nil

 	}

-	if s == string(types.BuilderBuildKit) {

+	switch types.BuilderVersion(s) {

+	case types.BuilderV1:

+		return types.BuilderV1, nil

+	case types.BuilderBuildKit:

 		return types.BuilderBuildKit, nil

+	default:

+		return "", errors.Errorf("invalid version %s", s)

 	}

-	return "", errors.Errorf("invalid version %s", s)

 }

 func (br *buildRouter) postPrune(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

@@ -205,7 +205,7 @@ const (

 	// BuilderV1 is the first generation builder in docker daemon

 	BuilderV1 BuilderVersion = "1"

 	// BuilderBuildKit is builder based on moby/buildkit project

-	BuilderBuildKit = "2"

+	BuilderBuildKit BuilderVersion = "2"

 )

 // ImageBuildResponse holds information