Yep you're right, v1.0.3 added logging which has exposed an old bug, there's an l.warn
a few lines above that which is the culprit (debug logging is off by default).
You're safe to ignore the warning. I have a fix for this, I'll release v1.0.4 later today.
Edit: 1.0.4 released, should fix this warning. I'm not at home, so I haven't updated GitHub, or tested it as much as I would like. It is a very small change so it should be OK, let me know if there are still problems.