This is an unintended side effect of a change to allow leading zeros to be preserved. It is already fixed for 3.6.8 (that change now requires opting in); 3.6.8 should be released soon. If you need an immediate fix you can either revert to 3.6.6 or download a 3.6.8 snapshot (I forget exactly where to find them off the top of my head)…(edit:)or, use pald0n’s suggested change.
Edit: When pasting error logs, it’s best to put a line containing only three tic-marks (```) before and after the error log text, to avoid having the forum software read special characters (like *) as formatting codes.