The change http://hg.openjdk.java.net/jdk9/dev/jdk/rev/d911fe42d2da to sun.security.provider.certpath.AlgorithmChecker has introduced an incompatibility to legacy JCE providers that would return old naming convention names, like SHA1/RSA, for X509Certificate.getSigAlgName().
Although the new naming such as SHA1withRSA should be implemented by the providers, it is safe to revert this place to take the signature algorithm name from the internal certificate implementation object that exists at this place anyway. By doing this we can overcome the potential incompatibility.