Skymaps bug when upgrading a project from U4 to U5

So, I downloaded U5 today, and found this error or bug, I don’t know what’s this, but yesterday on Unity4 I had not this problem, only when opened my project on Unity 5.

In PROJEKT select the skybox,which you are using. In the INSPECTOR you see that each of the 6 sides has a FIX NOW-Button. Fix it! Then skybox should be okay!