TAdvMemo versus horizontal scrollbar

When using TAdvMemo and adding a long text which needs horizontal scrollbars, the scrollbars are not visible after the following code:

AdvMemo1->Lines->Text = 'LONG TEXT';

Do I need to call some kind of formatting or component refresh after adding text?

I'm using C++ Builder XE2 Update 3 and TAdvMemo v2.3.12.0