diff --git a/src/cmd/diod.c b/src/cmd/diod.c
index 4051e5d5..1e4107b9 100644
--- a/src/cmd/diod.c
+++ b/src/cmd/diod.c
@@ -542,7 +542,7 @@ _test_setgroups (void)
         err_exit ("pthread_create");
     if ((err = pthread_join (t, NULL)))
         err_exit ("pthread_join");
-    if ((n = getgroups (ngroups_max, sg)) < 0)
+    if ((n = getgroups (NULL, 0)) < 0)
         err_exit ("getgroups");
     if (n == 0)
         rc = 1;