diff --git a/src/sock.c b/src/sock.c
index e5156b5..a60c406 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -363,6 +363,18 @@ ssize_t patty_ax25_sock_send(patty_ax25_sock *sock,
     uint8_t *buf = PATTY_AX25_FRAME_CONTROL_U(control)?
         sock->tx_buf: tx_slot(sock, sock->seq_send);
 
+    if (sock->iface == NULL) {
+        errno = ENETDOWN;
+
+        goto error_noif;
+    }
+
+    if (sock->remote.callsign[0] == '\0') {
+        errno = EBADF;
+
+        goto error_nopeer;
+    }
+
     if (toobig(sock, infolen)) {
         goto error_toobig;
     }
@@ -393,6 +405,8 @@ ssize_t patty_ax25_sock_send(patty_ax25_sock *sock,
 
 error_encode_address:
 error_toobig:
+error_nopeer:
+error_noif:
     return -1;
 }