diff --git a/src/engine/platform/sms.cpp b/src/engine/platform/sms.cpp
index 472038175..e4a0bedc2 100644
--- a/src/engine/platform/sms.cpp
+++ b/src/engine/platform/sms.cpp
@@ -228,6 +228,7 @@ void DivPlatformSMS::tick(bool sysTick) {
     if (parent->song.snNoLowPeriods) {
       if (chan[3].actualNote>0x5d) chan[3].freq=0x01;
     }
+    if (chan[3].freq<0) chan[3].freq=0;
     if (snNoiseMode&2) { // take period from channel 3
       if (updateSNMode || resetPhase) {
         if (snNoiseMode&1) {
diff --git a/src/engine/platform/t6w28.cpp b/src/engine/platform/t6w28.cpp
index 4578e79c3..5830b4283 100644
--- a/src/engine/platform/t6w28.cpp
+++ b/src/engine/platform/t6w28.cpp
@@ -146,6 +146,7 @@ void DivPlatformT6W28::tick(bool sysTick) {
     }
     if (chan[i].freqChanged || chan[i].keyOn || chan[i].keyOff) {
       chan[i].freq=snCalcFreq(i);
+      if (chan[i].freq<0) chan[i].freq=0;
       if (chan[i].freq>1023) chan[i].freq=1023;
       if (i==3) {
         rWrite(1,0x80|(2<<5)|(chan[3].freq&15));