diff --git a/src/conf.c b/src/conf.c
index 92f067a35..f06127834 100644
--- a/src/conf.c
+++ b/src/conf.c
@@ -559,6 +559,7 @@ static int frontend_set_conf(RIG *rig, token_t token, const char *val)
         }
 
         rs->pttport.parm.cm108.ptt_bitnum = val_i;
+        rs->rigport.parm.cm108.ptt_bitnum = val_i;
         rs->pttport_deprecated.parm.cm108.ptt_bitnum = val_i;
         break;
 
diff --git a/src/rig.c b/src/rig.c
index b65a54198..aa3be50d3 100644
--- a/src/rig.c
+++ b/src/rig.c
@@ -588,8 +588,13 @@ RIG *HAMLIB_API rig_init(rig_model_t rig_model)
      */
     case RIG_PORT_CM108:
         strncpy(rs->rigport.pathname, DEFAULT_CM108_PORT, HAMLIB_FILPATHLEN);
-        rs->rigport.parm.cm108.ptt_bitnum = DEFAULT_CM108_PTT_BITNUM;
-        rs->pttport.parm.cm108.ptt_bitnum = DEFAULT_CM108_PTT_BITNUM;
+
+        if (rs->rigport.parm.cm108.ptt_bitnum == 0)
+        {
+            rs->rigport.parm.cm108.ptt_bitnum = DEFAULT_CM108_PTT_BITNUM;
+            rs->pttport.parm.cm108.ptt_bitnum = DEFAULT_CM108_PTT_BITNUM;
+        }
+
         break;
 
     case RIG_PORT_GPIO: