CAS 6.2.x signing.key-size not working

[denizg]

Hello,

I am using cas overlay template and i have configured cas as oauth2 server. it works perfectly. but, when i change the jwt sign key size (default 512 https://github.com/apereo/cas/blob/master/api/cas-server-core-api-util/src/main/java/org/apereo/cas/util/crypto/CipherExecutor.java) to 256, this changes are not reflected. 

here is the config

cas.authn.oauth.access-token.crypto.signing.key=bBUhVvw9c2h2qwJd8hPRYatugQGGI4Xd
cas.authn.oauth.accessToken.crypto.signing.key-size=256

here is the error log

Caused by: org.jose4j.lang.InvalidKeyException: A key of the same size as the hash output (i.e. 512 bits for HS512) or larger MUST be used with the HMAC SHA algorithms but this key is only 256 bits

where am i missing? is it bug? thanks for response