diff --git a/minix/lib/libsys/ds.c b/minix/lib/libsys/ds.c
index 7f665e9b0..223f08302 100644
--- a/minix/lib/libsys/ds.c
+++ b/minix/lib/libsys/ds.c
@@ -141,6 +141,9 @@ static int ds_retrieve_raw(const char *ds_name, char *vaddr, size_t *length,
 	m.m_ds_req.val_len = *length;
 	m.m_ds_req.flags = flags;
 	r = do_invoke_ds(&m, DS_RETRIEVE, ds_name);
+	if (m.m_ds_reply.val_len > *length) {
+		return EINVAL;
+	}
 	*length = m.m_ds_reply.val_len;
 	cpf_revoke(gid);