I am working in an assembly that has two parts inserted.  The first part is a reference geometry part with one sketch.  This part was created outside of the assembly and inserted into the asssembly.  The second part was created inside (in-context) of the assembly.

I am trying to create relations between the midpoint of a line that is in a sketch inside of the (In-Context) part and an endpoint of a line in the reference geometry part.  I can select the midpoint of the line in the (In-Context) part but when I am unable to select the endpoint of the line in the reference geometry part.

Is there something I am missing?