import java.util.Base64;

public class StartsWithPadding {
    public static void main(String[] args) {
        Base64.getMimeDecoder().decode("$=#");
    }
}

A following case results to:
Exception in thread "main" java.lang.IllegalArgumentException: Input byte array has wrong 4-byte ending unit
at java.util.Base64$Decoder.decode0(Base64.java:1076)
at java.util.Base64$Decoder.decode(Base64.java:695)
at java.util.Base64$Decoder.decode(Base64.java:718)
at StartsWithPadding.main(StartsWithPadding.java:8)


This issue is reproducible in b87, looks like problem wasn't completely fixed.