According to this: http://issues.umbraco.org/issue/U4-7536, starting from v7.3.5, Umbraco should be able to single sign out. However, when I log in using my ASP.Net identity and then log out, I'm still only logged out of Umbraco, persisting the identity from my identity server. Are there any additional actions I need to take, to make it work? Below you can find my backoffice external authentication configuration.

var idAuth = new OpenIdConnectAuthenticationOptions
{
    Authority = "http://localhost:1234/logout",
    ClientId = "clientid",
    ClientSecret = "secret",
    RedirectUri = "http://localhost:7350/umbraco",
    ResponseType = "id_token token",
    Scope = "api",
    Caption = "Custom Identity",
    PostLogoutRedirectUri = "http://localhost:1234/logout",                        

    SignInAsAuthenticationType = Umbraco.Core.Constants.Security.BackOfficeExternalAuthenticationType
};

idAuth.ForUmbracoBackOffice("btn-custom", "icon-short_logo");

//ForUmbracoBackOffice prepends "Umbraco." before Auth type, so we need to set it again
idAuth.AuthenticationType = applicationConfiguration.AuthorityUrl;
var externalOptions = new ExternalSignInAutoLinkOptions(autoLinkExternalAccount: true);
externalOptions.OnAutoLinking = SetUserType;
idAuth.SetExternalSignInAutoLinkOptions(externalOptions);

app.UseOpenIdConnectAuthentication(idAuth);