diff --git a/src/sock.c b/src/sock.c
index cf77235..ef41686 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -509,6 +509,7 @@ error_invalid_type:
 static ssize_t frame_send(patty_ax25_sock *sock,
                           enum patty_ax25_frame_cr cr,
                           uint16_t control,
+                          uint8_t proto,
                           void *info,
                           size_t infolen) {
      size_t offset = 0;
@@ -547,7 +548,7 @@ static ssize_t frame_send(patty_ax25_sock *sock,
 
     if (info && infolen) {
         if (PATTY_AX25_FRAME_CONTROL_I(control)) {
-            buf[offset++] = (uint8_t)sock->proto;
+            buf[offset++] = proto;
         }
 
         memcpy(buf + offset, info, infolen);
@@ -628,6 +629,7 @@ ssize_t patty_ax25_sock_send_rr(patty_ax25_sock *sock,
     return frame_send(sock,
                       cr,
                       control_s(sock, PATTY_AX25_FRAME_RR, pf),
+                      0,
                       NULL,
                       0);
 }
@@ -638,6 +640,7 @@ ssize_t patty_ax25_sock_send_rnr(patty_ax25_sock *sock,
     return frame_send(sock,
                       cr,
                       control_s(sock, PATTY_AX25_FRAME_RNR, pf),
+                      0,
                       NULL,
                       0);
 }
@@ -648,6 +651,7 @@ ssize_t patty_ax25_sock_send_rej(patty_ax25_sock *sock,
     return frame_send(sock,
                       cr,
                       control_s(sock, PATTY_AX25_FRAME_REJ, pf),
+                      0,
                       NULL,
                       0);
 }
@@ -657,6 +661,7 @@ ssize_t patty_ax25_sock_send_srej(patty_ax25_sock *sock,
     return frame_send(sock,
                       cr,
                       control_s(sock, PATTY_AX25_FRAME_SREJ, 1),
+                      0,
                       NULL,
                       0);
 }
@@ -669,6 +674,7 @@ ssize_t patty_ax25_sock_send_sabm(patty_ax25_sock *sock, int pf) {
     return frame_send(sock,
                       PATTY_AX25_FRAME_COMMAND,
                       control_u(type, pf),
+                      0,
                       NULL,
                       0);
 }
@@ -677,6 +683,7 @@ ssize_t patty_ax25_sock_send_disc(patty_ax25_sock *sock, int pf) {
     return frame_send(sock,
                       PATTY_AX25_FRAME_COMMAND,
                       control_u(PATTY_AX25_FRAME_DISC, pf),
+                      0,
                       NULL,
                       0);
 }
@@ -715,6 +722,7 @@ ssize_t patty_ax25_sock_send_xid(patty_ax25_sock *sock,
     return frame_send(sock,
                       cr,
                       control_u(PATTY_AX25_FRAME_XID, 0),
+                      0,
                       buf,
                       encoded);
 
@@ -730,6 +738,7 @@ ssize_t patty_ax25_sock_send_test(patty_ax25_sock *sock,
     return frame_send(sock,
                       PATTY_AX25_FRAME_COMMAND,
                       control_u(PATTY_AX25_FRAME_TEST, 1),
+                      0,
                       info,
                       infolen);
 }
@@ -749,7 +758,12 @@ ssize_t patty_ax25_sock_write(patty_ax25_sock *sock,
         case PATTY_AX25_SOCK_STREAM:
             control = control_i(sock, 0);
 
-            if (frame_send(sock, PATTY_AX25_FRAME_COMMAND, control, buf, len) < 0) {
+            if (frame_send(sock,
+                           PATTY_AX25_FRAME_COMMAND,
+                           control,
+                           sock->proto,
+                           buf,
+                           len) < 0) {
                 goto error_frame_send;
             }
 
@@ -760,7 +774,12 @@ ssize_t patty_ax25_sock_write(patty_ax25_sock *sock,
         case PATTY_AX25_SOCK_DGRAM:
             control = control_ui(0);
 
-            if (frame_send(sock, PATTY_AX25_FRAME_COMMAND, control, buf, len) < 0) {
+            if (frame_send(sock,
+                           PATTY_AX25_FRAME_COMMAND,
+                           control,
+                           sock->proto,
+                           buf,
+                           len) < 0) {
                 goto error_frame_send;
             }