Wrong colors in 4.15P1

[anonymous_user_a21bc35f1 (anonymous_user_a21bc35f)]

I suspect my problem with an emissive material in 4.15 Pre is linked to this:

There is not the same “blooming glow” as in 4.14, even after I enter the recommended console command r.TonemapperFilm 0 to get the old behaviour.

Scenario: Blank Project in 4.14 and 4.15, a single cube with the following simple material:

This is what it looks like in 4.14:

And this is 4.15 after console command r.TonemapperFilm 0:

Any hints, please?