I know that JCL has problems when supplying nulls as log messages (NPE if I remember correctly) but I found out that slf4j copes with them nicely. I have a situation where stack trace contains all the information I need and I would like to misuse the message being null as a certain use case scenario, but I see that null gets the somewhat annoying String.valueOf(null) -> "null" treatment. I think more appropriate would be passing null values as null instead of string "null" since null /= "null"