MockMvc with session not working Spring 5

• Spring core: 5.0.1
• Spring test: 5.0.1
• Spring security: 5.0.0

I'm testing my rest-api using MockMvc. Everything was working fine with spring 4 and security 3, but since I updated along with the spring oauth2 as well it stopped working. My setup is really close to the ones we can find everywhere when it comes to mocking security, so I get the FilterChainProxy and I create the mockmvc with the filter chain

this.mockMvc = MockMvcBuilders.webAppContextSetup(wac)
        .addFilters(this.springSecurityFilterChain)
        .build();

Then I create the sessions like

public static MockHttpSession createSession(User user) {
    final OAuth2UserDetails oAuth2UserDetails = OAuth2UserDetails.builder()
            .withId(user.getId())
            .withUsername(user.getUsername())
            .withPassword(user.getPassword())
            .withClient(TEST_CLIENT.toString())
            .build();

    final UsernamePasswordAuthenticationToken token = new UsernamePasswordAuthenticationToken(
            oAuth2UserDetails, oAuth2UserDetails.getPassword(), oAuth2UserDetails.getAuthorities());

    MockHttpSession session = new MockHttpSession();
    session.setAttribute(HttpSessionSecurityContextRepository.SPRING_SECURITY_CONTEXT_KEY, new SecurityContextMock(token));

    return session;
}

And pass this session to mockmvc request like

    final MockHttpServletResponse result = mockMvc.perform(get(UrlStructure.SECURED_SUBSCRIPTIONS_V1)
            .contentType(MediaType.APPLICATION_JSON)
            .session(SecurityContextMock.createSession(validUser)))
            .andReturn()
            .getResponse();

But this not taken into consideration by the chain. I did some debugging and the context holder doesn't hold any context at all. I already tried setting it manually as well and it just doesn't work.

Again this setup was working before with the previous versions, what changed exactly?