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How to extend Constructor Injection?

Suppose I have MyClass with a very simple dependency. It uses constructor injection.

public class MyClass : IMyClass
    private IA A;

    public MyClass(IA a)
        A = a;

This code get shipped and some other developers are using it.
At some point in the future I need to add in a second dependency, on IB.

How should I add this dependency on IB?

Some options, and why I disapprove:

  • Just add it to the constructor
    • Braking change.
  • Inheritance or the decorator pattern.
    • Extra classes and code bloat.
    • New class will have boilerplate code passing around the IA.
    • I have no guarantee that other developers will switch to using the new class.
  • Use a service locator to populate the new IB field.
    • I'm now using two different types of injection for extra confusion.

It seems to me that constructor injection is just not easily extensible.