pushing an unsolicited response to an artifact endpoint

[Tom Scavo]

I'm trying to use the Shib2 unsolicited SSO feature with the artifact
binding. Has anyone used these two together successfully?

I've tried multiple combinations of IdP and SP. For example:

https://idp.incommonfederation.org/idp/profile/SAML2/Unsolicited/SSO?providerId=https%3A%2F%2Fservice1.internet2.edu%2Fshibboleth&shire=https%3A%2F%2Fservice1.internet2.edu%2FShibboleth.sso%2FSAML2%2FArtifact

In all of the cases I've tried, I get the following error message (in
the browser window):

opensaml::BindingException at
(https://service1.internet2.edu/Shibboleth.sso/SAML2/Artifact)
Unable to resolve artifact(s) into a SAML response.

Any idea what's going on?

Thanks,
Tom