QIcon::setThemeName(QIcon::themeName()); needs to be called to display Adwaita icon on KDE Plasma

Hello, I was trying on KDE Plasma 5.25 to display an icon in C++ using:

QIcon icon = QIcon::fromTheme("window-close-symbolic");

This works for every icon theme I tried, except for Adwaita. I managed, however, to get the Adwaita icon to display by preceding the above with:

QIcon::setThemeName(QIcon::themeName());

This seems an odd thing to have to do.