2D animation : problem with rotation interpolation

Hi everyone,

In a motion with 2D sprites, I got some key points with different rotations (only the z is changed). I want an instant modification, so I choose Broken with Both tangents : Constant, but 1 or 2 frames before a key point it makes a little interpolation before set the correct value, for example for 0 to 180, in the 2 frames before 180 the value is around 5 and 7. I tried both Quaternion and Euler Angles in the Interpolation property, it doesn't change anything.

Has someone a solution for this ? Or do I have do change the rotation in another way, maybe with a trigger which set the local rotation ?

Thanks in advance.

PS : sorry for my bad english