Cannot acces ActivityCompatApi23 when trying to use FragmentActivity

I just experienced a similar issue when using AppCompatActivity:

error: cannot access ActivityCompatApi23

I fixed by setting a specific support library version:

compile 'com.android.support:appcompat-v7:26.+' <-- Old
compile 'com.android.support:appcompat-v7:26.0.2' <-- New

Following Eugen Pechanec's explanation (as a comment below the original post) fixed the problem for me:

All support libraries need to be same version. If your compile SDK is 25, it's 25.4.0. If your compile SDK is 26, it's 26.0.1. Don't mix them.