Breeding of genetically polled animals is a desirable approach in modern cattle husbandry for welfare and economic reasons. At least four different genetic variants associated with polledness in cattle have been identified, suggesting genetic heterogeneity. These dominant variants are located on chromosome 1 between approximately 2.42-2.73 Mb (reference: ARS-UCD1.3), also called the POLLED locus. Among these variants, Friesian (P Here, we conduct whole-genome sequencing analyses of two trios exhibiting unexpected inheritance patterns related to the P We show that different genomic arrangements in the POLLED locus can lead to the emergence of de novo ancestral horn phenotypes. Such arrangements can complicate phenotype prediction in offspring, even when sires or dams have been tested as genetically homozygous polled. Therefore, it is important, for a better understanding of the relationship between the POLLED locus and the POLLED phenotype, that any deviation from the expected result is critically analysed. Possibly, some of these cases can further narrow down the sequence motif that is essential for polledness in cattle.