What could cause the original 'OAuth2' state parameter to be null in org.springframework.social.connect.web.ConnectSupport?

I am trying to use Spring Social on my application and I noticed while debugging that the original 'OAuth2' state parameter is always null on my app.

See Spring Social source code for org.springframework.social.connect.web.ConnectSupport below:

private void verifyStateParameter(NativeWebRequest request) {
    String state = request.getParameter("state");
    String originalState = extractCachedOAuth2State(request);//Always null...
    if (state == null || !state.equals(originalState)) {
        throw new IllegalStateException("The OAuth2 'state' parameter is missing or doesn't match.");
    }
}

private String extractCachedOAuth2State(WebRequest request) {
    String state = (String) sessionStrategy.getAttribute(request, OAUTH2_STATE_ATTRIBUTE);
    sessionStrategy.removeAttribute(request, OAUTH2_STATE_ATTRIBUTE);
    return state;       
}

Can anyone please help?

edit: I do see the state parameter being passed back by facebook:

Request URL:https://www.facebook.com/v2.5/dialog/oauth?client_id=414113641982912&response_type=code&redirect_uri=http%3A%2F%2Flocalhost%3A8080%2Fconnect%2Ffacebook&scope=public_profile&state=0b7a97b5-b8d1-4f97-9b60-e3242c9c7eb9
Request Method:GET
Status Code:302 
Remote Address:179.60.192.36:443

edit 2: By the way, the exception I get is the following:

Exception while handling OAuth2 callback (The OAuth2 'state' parameter is missing or doesn't match.). Redirecting to facebook connection status page.

It turned out that the issue was caused by the fact that I was relying on headers - as opposed to cookies - to manage the session.

By commenting out the following spring session configuration bean:

@Bean
public HttpSessionStrategy sessionStrategy(){
    return new HeaderHttpSessionStrategy();
}

The oauth2 state parameter issue was sorted.

P.S. Now I have got to find a way to get Spring Social to work with my current configuration of Spring Session...

Edit: I managed to keep the HeaderHttpSessionStrategy (on the spring session side) and get it to work by implementing my own SessionStrategy (on the spring social side) as follows:

public class CustomSessionStrategy implements SessionStrategy {

    public void setAttribute(RequestAttributes request, String name, Object value) {
        request.setAttribute(name, value, RequestAttributes.SCOPE_SESSION);
    }

    public Object getAttribute(RequestAttributes request, String name) {
        ServletWebRequest servletWebRequest = (ServletWebRequest) request;
        return servletWebRequest.getParameter(name);
    }

    public void removeAttribute(RequestAttributes request, String name) {
        request.removeAttribute(name, RequestAttributes.SCOPE_SESSION);
    }
}