emberjs set deeply nested undefined key

I have a model with a property response, containing a json with various keys and nesting levels

I can bind an input field to a one level missing key, but not more

for example if after loading the model

model.response = { key1: { c1: 12} }

naturally, I can do

and see 12 in the input field

but, I can do

which will be recorded when I save the model, and found on page reload

but I cannot do

with two levels of missingness.

Not only the value is not saved, but also a computed property with dependent key 'reponse.misskey1.miss2' on the model is never triggered on input change

Do I need to set all missing keys or is there any other way to make it work ?

In this situation, shall I use unknwonProperty handler ?

Thanks