Index: virtinst/buildconfig.py
--- virtinst/buildconfig.py.orig
+++ virtinst/buildconfig.py
@@ -62,7 +62,7 @@ class _BuildConfig(object):
         self.icon_dir = None
         self.gsettings_dir = None
         self.running_from_srcdir = _running_from_srcdir
-        self._set_paths_by_prefix(_get_param("prefix", "/usr"))
+        self._set_paths_by_prefix(_get_param("prefix", "${PREFIX}"))
 
 
     def _set_paths_by_prefix(self, prefix):