CA2213 warning when using ?. (null-conditional Operator) to call Dispose

I'm implementing IDisposable, and in my Dispose() method when calling Dispose() on other managed resources I'm using the ?. operator like so:

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if(disposing)
        {
            _ChangeLock?.Dispose();
        }
    }

I'm still getting the following code analysis error:

CA2213: 'MyClass' contains field 'MyClass._ChangeLock' that is of IDisposable type: 'ReaderWriterLockSlim'. Change the Dispose method on 'MyClass' to call Dispose or Close on this field.

If I change to a standard null check, the code analysis warning goes away:

if(_ChangeLock != null)
    _ChangeLock.Dispose();

Is there something wrong with using the null-conditional operator the way I am, or is this code analysis rule outdated, or what?