I haven't tested it, but it might be that this spell is not upcastable.
Just did ... and it really isnt.

Wich is of course wrong. :-/
On a related note, I actually like the homebrew of learning more cantrips. It makes no sense a Wizard can learn all leveled spells but not all cantrips.
Agreed ...
Even tho, if someone would like to replace that with "Cantrip Formulas" (via.
http://dnd5e.wikidot.com/wizard) i would not mind that one either.
