--- /dev/null
+http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=492827
+Patch by Neil Brown
+
+diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
+index f555dcc..48d737b 100644
+--- a/utils/mountd/cache.c
++++ b/utils/mountd/cache.c
+@@ -158,7 +158,8 @@ void auth_unix_gid(FILE *f)
+ qword_printint(f, ngroups);
+ for (i=0; i<ngroups; i++)
+ qword_printint(f, groups[i]);
+- }
++ } else
++ qword_printint(f, 0);
+ qword_eol(f);
+ if (groups != glist)
+ free(groups);