diff --git a/PDP11/pdp11_ch.c b/PDP11/pdp11_ch.c
index 80a2c432..03a88e6f 100644
--- a/PDP11/pdp11_ch.c
+++ b/PDP11/pdp11_ch.c
@@ -419,8 +419,9 @@ t_stat ch_attach (UNIT *uptr, CONST char *cptr)
   if (peer[0] == '\0')
     return sim_messagef (SCPE_2FARG, "Must set Chaosnet PEER \"SET CH PEER=host:port\"\n");
 
-  sprintf (linkinfo, "Buffer=%d,Line=%d,UDP,%s,PACKET,Connect=%s",
-           (int)sizeof tx_buffer, 0, cptr, peer);
+  linkinfo[sizeof (linkinfo) - 1] = '\0';
+  snprintf (linkinfo, sizeof (linkinfo) - 1, "Buffer=%d,Line=%d,UDP,%s,PACKET,Connect=%s",
+           (int)sizeof (tx_buffer), 0, cptr, peer);
   r = tmxr_attach (&ch_tmxr, uptr, linkinfo);
   if (r != SCPE_OK) {
     sim_debug (DBG_ERR, &ch_dev, "TMXR error opening master\n");