--- a/gtweak/tweaks/tweak_group_appearance.py
+++ b/gtweak/tweaks/tweak_group_appearance.py
@@ -93,7 +93,7 @@
         valid = walk_directories(dirs, lambda d:
                     os.path.isdir(d) and \
                         os.path.exists(os.path.join(d, "cursors")))
-        return valid
+        return set(valid)
 
 class ShellThemeTweak(Gtk.Box, Tweak):
 
