RelayState missing from SAML response


We have an application set up with SSO. I can successfully sign in using both binding types, but the RelayState from our request isn’t carried through to the SAML response sent back to our ACS URL.

Using a default RelayState value in Okta works. I’ve also posted a SAML response to myself locally with a simple form, and the RelayState worked there too.

When using the HTTP redirect binding our query string is

When using the HTTP post binding our form is

<!DOCTYPE html>
    <title>Single Sign On</title>
    <script type="text/javascript">
        window.onload = function () { document.forms[0].submit(); }
<form method="post" action="...">
    <input type="hidden" value="test" name="RelayState" id="RelayState" />
    <input type="hidden" value="PHNhbWx...UmVxdWVzdD4%3d" name="SAMLRequest" id="SAMLRequest" />

Both methods work for signing in, just not passing on the RelayState.

Any help would be appreciated.