An incumbent Senedd member, Michelle Brown, has been left off some ballot papers for the Gogledd Cymru region.
Ms Brown is standing as an independent candidate after being elected to the Senedd to represent the United Kingdom Independence Party (UKIP) in 2016.
Some voting papers in Ynys Môn and Arfon did not include ms Brown's name, but returning officers said that voters would be presented with the full range of candidates regardless.
Voters are also being advised of this error as they attend their polling stations.
Correct ballot papers are now being issued across the region.