--- a/gwlib/utils.c.old	2016-08-25 18:52:59.944949612 +0200
+++ b/gwlib/utils.c	2016-08-25 18:53:30.352659566 +0200
@@ -387,7 +387,7 @@
     }
 
 #ifndef __INTERIX
-    if (initgroups(user, -1) == -1) {
+    if (initgroups(user, pass->pw_gid) == -1) {
         error(errno, "Could not set supplementary group ID's.");
     }
 #endif
