diff --git a/lib/chibi/system.sld b/lib/chibi/system.sld
index 49e500f3..fe2b579a 100644
--- a/lib/chibi/system.sld
+++ b/lib/chibi/system.sld
@@ -3,7 +3,7 @@
   (export get-host-name
           user? user-name user-password
           user-id user-group-id user-gecos user-home user-shell
-          group-name group-password group-id
+          group? group-name group-password group-id
           current-user-id current-group-id
           current-effective-user-id current-effective-group-id
           set-current-user-id! set-current-effective-user-id!