C# / Error (CS0122) / Class not accessible in scripting component

Hi

using VS2017 and the very helpful template I have developed a C# component for GH which uses another class in the same namespace. This component works.

Now I want to use the very same class in the C# scripting component. I have added the assembly information and the automatic code completion actually "sees" the class, providing information regarding available constructors etc. But the script does not run, there seems to be some access restrictions:

Error (CS0122): Der Zugriff auf 'MyClass' ist aufgrund der Sicherheitsebene nicht möglich.

Help is very much appreciated!