REST Assured: how to test object of type "Set" in body?

I want to test the value of hole set with .body sentence in REST Assured. when i use this code only get some error...

BannerDto resultBannerDto = given()
            .contentType("application/json")
            .body(bannerAddDto)
            .when()
            .post("/api/v1/admin/banners")
            .then()
            .statusCode(HttpStatus.OK.value())
            .contentType(ContentType.JSON)
            .body("name", equalTo("banner A"))
//this line make error:
            .body("regions", equalTo(regionsSet.toString()))
            .extract().as(BannerDto.class);

while error is:

java.lang.AssertionError: 1 expectation failed.
JSON path regions doesn't match.
Expected: [1, 2]
Actual: [1, 2]

parameter regionsSet is:

    private Set<Long> regionsSet = new HashSet<>();
    regionsSet.add(1l);
    regionsSet.add(2l);

and original response is:

Actual: {regions=[1, 2], endDate=2017-05-01T22:00:00, productIds=[], bannerId=15,...

please help me find out whats wrong?