diff --git a/sim_tmxr.c b/sim_tmxr.c
index 3a9900b2..609180da 100644
--- a/sim_tmxr.c
+++ b/sim_tmxr.c
@@ -1411,7 +1411,7 @@ if (lp->mp && lp->modem_control) {                  /* This API ONLY works on mo
         if (lp->serport)
             return sim_control_serial (lp->serport, bits_to_set, bits_to_clear, incoming_bits);
         if ((lp->sock) || (lp->connecting)) {
-            if (bits_to_clear&TMXR_MDM_DTR) {           /* drop DTR? */
+            if ((~before_modem_bits & bits_to_clear & TMXR_MDM_DTR) != 0) { /* drop DTR? */
                 if (lp->sock)
                     tmxr_report_disconnection (lp);     /* report closure */
                 tmxr_reset_ln (lp);
@@ -1431,6 +1431,13 @@ if (lp->mp && lp->modem_control) {                  /* This API ONLY works on mo
         }
     return SCPE_OK;
     }
+if ((lp->sock) || (lp->connecting)) {
+    if ((~before_modem_bits & bits_to_clear & TMXR_MDM_DTR) != 0) { /* drop DTR? */
+        if (lp->sock)
+            tmxr_report_disconnection (lp);     /* report closure */
+        tmxr_reset_ln (lp);
+        }
+    }
 if ((lp->serport) && (!lp->loopback))
     sim_control_serial (lp->serport, 0, 0, incoming_bits);
 return SCPE_IERR;