Pan doesnt have father surname but in form 32 it is mandator

while filling INC form 32, they are asking father first and last name but to validate the PAN we should give detail as per PAN, so in my case the client doesnt have any surname for his father as per PAN and PAN is getting validated but while clicking the CHECK butoon at the bottom of form it is asking mandatorily to fill surname of father.
how to go ahead if i give surname then the PAN detail wont get validated

plz expert help in this matter