diff --git a/src/demod/DemodulatorInstance.cpp b/src/demod/DemodulatorInstance.cpp
index c3440bc..b03ece4 100644
--- a/src/demod/DemodulatorInstance.cpp
+++ b/src/demod/DemodulatorInstance.cpp
@@ -255,7 +255,9 @@ void DemodulatorInstance::setOutputDevice(int device_id) {
 
 int DemodulatorInstance::getOutputDevice() {
     if (currentOutputDevice == -1) {
-        currentOutputDevice = audioThread->getOutputDevice();
+        if (audioThread) {
+            currentOutputDevice = audioThread->getOutputDevice();
+        }
     }
 
     return currentOutputDevice;
@@ -308,7 +310,7 @@ void DemodulatorInstance::setBandwidth(int bw) {
             bw = AudioThread::deviceSampleRate[getOutputDevice()];
         }
     }
-    if (!active) {
+    if (!active && demodulatorPreThread != NULL) {
         currentBandwidth = bw;
         checkBandwidth();
         demodulatorPreThread->getParams().bandwidth = currentBandwidth;
diff --git a/src/visual/WaterfallCanvas.cpp b/src/visual/WaterfallCanvas.cpp
index 704f411..8d48418 100644
--- a/src/visual/WaterfallCanvas.cpp
+++ b/src/visual/WaterfallCanvas.cpp
@@ -79,6 +79,7 @@ void WaterfallCanvas::processInputQueue() {
     double targetVis =  1.0 / (double)linesPerSecond;
     lpsIndex += gTimer.lastUpdateSeconds();
 
+    bool updated = false;
     if (linesPerSecond) {
         if (lpsIndex >= targetVis) {
             while (lpsIndex >= targetVis) {
@@ -90,6 +91,7 @@ void WaterfallCanvas::processInputQueue() {
                         waterfallPanel.setPoints(vData->spectrum_points);
                         waterfallPanel.step();
                         vData->decRefCount();
+                        updated = true;
                     }
                     lpsIndex-=targetVis;
                 } else {
@@ -98,10 +100,11 @@ void WaterfallCanvas::processInputQueue() {
             }
         }
     }
-    wxClientDC(this);
-    glContext->SetCurrent(*this);
-    waterfallPanel.update();
-    
+    if (updated) {
+        wxClientDC(this);
+        glContext->SetCurrent(*this);
+        waterfallPanel.update();
+    }
     tex_update.unlock();
 }