Change text at top of INSTFILES page XPUI

I am trying to change the text when the INSTFILES page finishes. It currently says "All components of 'MyApp' were successfully copied to your computer"

I just want it to says its finished, not necessarily successfully.

I am using the ExperienceUI with a WAnsis skin.
This is the code that I am thinking should do it. But doesn't work for some reason.

   !define XPUI_INSTSUCCESSPAGE_TEXT_TOP "The installation process has completed. Please click Next."

${Page} INSTFILES

I have also tried

LangString XPUI_INSTSUCCESSPAGE_TEXT_TOP ${LANG_ENGLISH} "The installation process has completed. Please click Next."

with no success