We applied a minor update to the CGenFF program - the new version is 0.9.1 . This version has improved functionality for renumbering atoms with duplicate names; the renumbering algorithm in version 0.9.0 in rare cases behaved incorrectly. It also has some minor improvements in the warning and error messages and in the treatment of spiro compounds. Just like version 0.9.0, version 0.9.1 of the CGenFF program requires version 2b6 of the CGenFF Force Field.