Filtering by customer__firstName-customer__lastName-icontains not allowed

[aywein]

I implemented fiter using
get_icontains_input_filter(title_='Customer', attrs=('customer__firstName', 'customer__lastName')),
but i get an error when I search
Filtering by customer__firstName-customer__lastName-icontains not allowed

Note: if I filter just by ustomer__firstName or just by customer__lastName it works