> repeating same code seems a bad idea

DRY is not a golden rule that overrides all other programming principles - it's intended to prevent you from repeating actual code (multiple assignments, a computation, conditionals, flow control, etc.) but repeating one statement is sometimes necessary and/or better than over-abstracting in the name of DRY-ness.

Add another protected method to the base-class and you will *still* have a single statement - now it's just a function call rather than an assignment. You're still repeating a statement - doesn't make your code more DRY.

Moreover, repeating a single assignment or function-call is extremely unlikely to cause any serious maintenance problems.