How to sign security tokens using SHA256 in WIF STS?

Question

I am using Thinktecture STS and would like to sign the issued tokens using SHA256 instead of SHA1? I tried adding the algorithm to the application using:

CryptoConfig.AddAlgorithm(
         typeof(RSAPKCS1SHA256SignatureDescription),
         "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256");

But it starts giving error:

Invalid algorithm specified

Knowing that the certificate I am using is compatible with SHA256. Any idea?