--- a/src/xdp-portal-impl.c
+++ b/src/xdp-portal-impl.c
@@ -277,6 +277,8 @@ load_installed_portals (gboolean opt_verbose)
 
   /* We need to override this in the tests */
   portal_dir = g_getenv ("XDG_DESKTOP_PORTAL_DIR");
+  if (portal_dir == NULL)
+    portal_dir = g_getenv ("NIX_XDG_DESKTOP_PORTAL_DIR");
   if (portal_dir != NULL)
     {