The photospheric Mn I 539.4 nm line in the solar spectrum shows unusual variability with the solar cycle in that its depth decreases with increasing activity. citet{nv-2001A&A...369L..13D} claimed that this phenomenon is due to interlocking between the chromospheric Mg II h & k lines and an overlapping Mn I multiplet. In this contribution we test this hypothesis by synthesizing Mn I 539.4 nm line including these interlocking lines for a range of standard solar models and then combining resulting profiles without and with interlocking to emulate the full-disk profile variation. We find that the interlocking gives only a minor contribution; the largest one comes from different temperature stratifications in the photospheric layers of the various models.