diff --git a/src/engine/platform/gb.cpp b/src/engine/platform/gb.cpp
index 222191f6c..3b9d2d2c6 100644
--- a/src/engine/platform/gb.cpp
+++ b/src/engine/platform/gb.cpp
@@ -308,7 +308,9 @@ int DivPlatformGB::dispatch(DivCommand c) {
       chan[c.chan].note=c.value;
       break;
     case DIV_CMD_PRE_PORTA:
-      chan[c.chan].std.init(parent->getIns(chan[c.chan].ins));
+      if (chan[c.chan].active) {
+        chan[c.chan].std.init(parent->getIns(chan[c.chan].ins));
+      }
       chan[c.chan].inPorta=c.value;
       break;
     case DIV_CMD_GB_SWEEP_DIR:
diff --git a/src/engine/platform/sms.cpp b/src/engine/platform/sms.cpp
index e1c806770..ed0838038 100644
--- a/src/engine/platform/sms.cpp
+++ b/src/engine/platform/sms.cpp
@@ -33,14 +33,16 @@ void DivPlatformSMS::tick() {
       rWrite(0x90|(i<<5)|(isMuted[i]?15:(15-(chan[i].outVol&15))));
     }
     if (chan[i].std.hadArp) {
-      if (chan[i].std.arpMode) {
-        chan[i].baseFreq=NOTE_PERIODIC(chan[i].std.arp);
-        chan[i].actualNote=chan[i].std.arp;
-      } else {
-        chan[i].baseFreq=NOTE_PERIODIC(chan[i].note+chan[i].std.arp);
-        chan[i].actualNote=chan[i].note+chan[i].std.arp;
+      if (!chan[i].inPorta) {
+        if (chan[i].std.arpMode) {
+          chan[i].baseFreq=NOTE_PERIODIC(chan[i].std.arp);
+          chan[i].actualNote=chan[i].std.arp;
+        } else {
+          chan[i].baseFreq=NOTE_PERIODIC(chan[i].note+chan[i].std.arp);
+          chan[i].actualNote=chan[i].note+chan[i].std.arp;
+        }
+        chan[i].freqChanged=true;
       }
-      chan[i].freqChanged=true;
     } else {
       if (chan[i].std.arpMode && chan[i].std.finishedArp) {
         chan[i].baseFreq=NOTE_PERIODIC(chan[i].note);
@@ -163,7 +165,10 @@ int DivPlatformSMS::dispatch(DivCommand c) {
         }
       }
       chan[c.chan].freqChanged=true;
-      if (return2) return 2;
+      if (return2) {
+        chan[c.chan].inPorta=false;
+        return 2;
+      }
       break;
     }
     case DIV_CMD_STD_NOISE_MODE:
@@ -178,6 +183,7 @@ int DivPlatformSMS::dispatch(DivCommand c) {
       break;
     case DIV_CMD_PRE_PORTA:
       chan[c.chan].std.init(parent->getIns(chan[c.chan].ins));
+      chan[c.chan].inPorta=c.value;
       break;
     case DIV_CMD_GET_VOLMAX:
       return 15;
diff --git a/src/engine/platform/sms.h b/src/engine/platform/sms.h
index 5eced7ed6..85af1a18c 100644
--- a/src/engine/platform/sms.h
+++ b/src/engine/platform/sms.h
@@ -9,7 +9,7 @@ class DivPlatformSMS: public DivDispatch {
   struct Channel {
     int freq, baseFreq, pitch, note, actualNote;
     unsigned char ins;
-    bool active, insChanged, freqChanged, keyOn, keyOff;
+    bool active, insChanged, freqChanged, keyOn, keyOff, inPorta;
     signed char vol, outVol;
     DivMacroInt std;
     Channel():
@@ -24,6 +24,7 @@ class DivPlatformSMS: public DivDispatch {
       freqChanged(false),
       keyOn(false),
       keyOff(false),
+      inPorta(false),
       vol(15),
       outVol(15) {}
   };
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index 0232735ac..e8383d8d9 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -551,6 +551,7 @@ void DivEngine::processRow(int i, bool afterDelay) {
           chan[i].portaNote=-1;
           chan[i].portaSpeed=-1;
           chan[i].inPorta=false;
+          dispatchCmd(DivCommand(DIV_CMD_PRE_PORTA,i,false));
         } else {
           chan[i].portaNote=song.limitSlides?disCont[dispatchOfChan[i]].dispatch->getPortaFloor(dispatchChanOfChan[i]):-60;
           chan[i].portaSpeed=effectVal;
@@ -559,6 +560,7 @@ void DivEngine::processRow(int i, bool afterDelay) {
           chan[i].stopOnOff=false;
           chan[i].scheduledSlideReset=false;
           chan[i].inPorta=false;
+          dispatchCmd(DivCommand(DIV_CMD_PRE_PORTA,i,true));
         }
         break;
       case 0x03: // portamento