How to sign a custom JCE security provider

Question

Sun's PKCS11 JCE security provider is lacking some functionality we need.
So I wrote an enhanced version of it using the original sources.

Unfortunately the JCE infrastructure rejects the new provider
"JCE cannot authenticate the provider"
because it is not properly signed.

javax.crypto.JceSecurity.verifyProviderJar(...) throws.
(it calls javax.crypto.JarVerifier.verify())

Any suggestions how to sign the new provider to make it work with JCE?