diff --git a/src/sock.c b/src/sock.c
index 47ba896..d60db09 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -56,18 +56,20 @@ static inline size_t rx_bufsz(patty_ax25_sock *sock) {
     return PATTY_AX25_FRAME_OVERHEAD + sock->n_maxlen_rx;
 }
 
+static inline size_t tx_slots(patty_ax25_sock *sock) {
+    return sock->mode == PATTY_AX25_SOCK_SABME? 128: 8;
+}
+
 static inline size_t tx_slot_size(patty_ax25_sock *sock) {
     return sizeof(struct slot) + PATTY_AX25_FRAME_OVERHEAD + sock->n_maxlen_tx;
 }
 
 static inline size_t tx_slots_size(patty_ax25_sock *sock) {
-    size_t slots = sock->mode == PATTY_AX25_SOCK_SABME? 128: 8;
-
-    return slots * tx_slot_size(sock);
+    return tx_slots(sock) * tx_slot_size(sock);
 }
 
 static inline int tx_seq(patty_ax25_sock *sock, int seq) {
-    return sock->mode == PATTY_AX25_SOCK_SABME? seq % 128: seq % 8;
+    return seq % tx_slots(sock);
 }
 
 static inline struct slot *tx_slot(patty_ax25_sock *sock, int seq) {