diff --git a/kadmin/kadm_conn.c b/kadmin/kadm_conn.c
index 59d8dafef..4046893e6 100644
--- a/kadmin/kadm_conn.c
+++ b/kadmin/kadm_conn.c
@@ -172,6 +172,8 @@ wait_for_connection(krb5_context context,
     FD_ZERO(&orig_read_set);
     
     for(i = 0; i < num_socks; i++) {
+	if (socks[i] >= FD_SETSIZE)
+	    errx (1, "fd too large");
 	FD_SET(socks[i], &orig_read_set);
 	max_fd = max(max_fd, socks[i]);
     }