CanvasRenderer OnEnable SetAlpha

I am using the CanvasRenderer.SetAlpha() function to fade out UI elements. It works well most of the time, but at one position I deactivate gemeobjects, and when they are activated again, the CanvasRenderer's alpha value is reset to 1 instead of keeping the value it had before. Is that the intended behaviour?

Edit: A short test tells me it already happens in OnDisable() (or earlier, Debug.Log in OnDisable returns 1, while in Update it prints the correct value)