EE : No lastname in former name


In my education documents and previous passport, I only had first name (NO last name).
Later I went thru name change process and applied a new passport with first name and last name.

Now I have got an ITA and while submitting the details, I have to enter any former names.
But while entering former name I notice that both first name and last name is mandatory.

It does NOT allow me to leave the first name blank as mentioned here:

What to do in this case? How to enter the former name? Please advise.



I dont think name change means adding missing last name.