Activator.CreateInstance and passing a boxed object to an invoked method

I have the following code ...

My Command handler:

public class MyHandler : IHandler
{
  // I Want to get rid of this method
  public override void ExecuteOperation(BaseOperation operation)
  {
    // This is a work-around
    this.ExecuteOperation(operation as SpecificOperation);
  }

  public override void ExecuteOperation(SpecificOperation operation)
  {
    // Do actual work here
  }
}

My Command handler dispatcher:

private dynamic FindOperationHandler(TBaseProvisioningOperation operation)
{
  ... some logic here
  return Activator.CreateInstance(handlerType, ... args here ...)
}

My consumer code

public void PerformProvisioningOperation(BaseOperation operation)
{
  // Find the correct handler for this operation
  var operationHandler = this.FindOperationHandler(operation as TBaseProvisioningOperation);

  // make it execute the operation
  // NOTE: 'operation' is SpecificOperation type, for example
  operationHandler.ExecuteOperation(operation); // <--- problem is here
}

The issue is that when I create an instance of my handler class with the Activator.CreateInstance and pass it a boxed object (i.e. as "BaseOperation") parameter, .NET looks for a method in the handler, which has a parameter of the base type, instead of automatically invoking the one which can handle the object if it were unboxed (i.e. explicitly cast).

Of course we have SpecificOperation : BaseOperation

In other words: I want when I execute operationHandler.ExecuteOperation(operation);, .NET to invoke ExecuteOperation(SpecificOperation operation) instead of ExecuteOperation(BaseOperation operation), because the operation parameter is boxed (i.e. it IS SpecificOperation but is downcast-ed as BaseOperation).

How do I achieve that?