Rest-assured: java.lang.ClassCastException: io.restassured.path.xml.XmlPath cannot be cast to java.l

@Test
        public void request(){
        System.setProperty("javax.net.ssl.trustStore", "/Users/qiangma/APItest180415/jssecacerts");

        String title =
                    given()
                            .queryParam("q", "appium")
                    .when()
                            .get("https://testerhome.com/search").prettyPeek() 
                    .then()
                            .statusCode(200)
                    .extract()
                            .path("html.head.title")
                            .toString() //解决报错：java.lang.ClassCastException: io.restassured.path.xml.XmlPath cannot be cast to java.lang.String
                    ;

            System.out.println(title);
        }