Index: meson.build
--- meson.build.orig
+++ meson.build
@@ -22,8 +22,8 @@ includedir          = get_option('includedir')
 incdir              = 'irssi'
 moduledir           = get_option('libdir') / incdir / 'modules'
 helpdir             = get_option('datadir') / incdir / 'help'
-themedir            = get_option('datadir') / incdir / 'themes'
-scriptdir           = get_option('datadir') / incdir / 'scripts'
+themedir            = '${SYSCONFDIR}' / incdir / 'themes'
+scriptdir           = '${SYSCONFDIR}' / incdir / 'scripts'
 docdir              = get_option('docdir') != '' ? get_option('docdir') : (get_option('datadir') / 'doc' / incdir)
 
 want_textui         = get_option('without-textui') != 'yes'