Hi, I was recently doing a code review for a coworker and saw that he was concatenating strings and not using the varargs method of building the log message. I asked him why he was doing that and he explained it was because he also had a Throwable that he wanted to be passed as argument to see the stacktrace. He was not aware of the change in SLF4J 1.6.0 which allows us to pass a Throwable as last argument to the varargs. "Unfortunately", when I was showing him implementations of this, I encountered the slf4j EventRecordingLogger and this implementation of the slf4j logger does not comply with this "new" behaviour. However I'm not sure if this is intentional. Assuming it's not intentional, I've created a fork and I've made the required changes. But before I spend "days" on this while it's intentional I thought: let's write a quick email about this and ask for guidance. I also saw that in the case of 2 Object arguments, the MessageFormatter seems to be suboptimal and is creating more objects then strictly required. For the 1 Object argument case it it's also doing too much, certainly in case someone calls it with a Throwable. I've now added a runtime check to it. Since overloading it with a Throwable version will change the way the method behaves in case the caller does not know if it's being given a Throwable or an Object. It would be very illogical to call this method with a Throwable, with the 1.6 way of dealing with Throwables, since what do you want to format then? But with the runtime check people won't loose their stacktraces, and otherwise in case the MessageFormatter is being used in a wrong way people will see their stacktraces being converted into one line because of a (minor? it's one instanceof call too many per call to the one Object logger variant) performance optimization. I've not yet created the test cases for the EventRecordingLogger, I'll do that in case it's indeed unintentional that it's loosing the Throwables. I've added two tests for the changes I made to the MessageFormatter. While I was at it I also applied some improvements IntelliJ suggested. You can see my changes on my fork: https://github.com/qos-ch/slf4j/compare/master...delgurth:eventrecordinglogg... I hope you are able to review my changes and shed your light on it. Kind regards, Wessel van Norel