diff --git a/src/frontend/qt_sdl/main.cpp b/src/frontend/qt_sdl/main.cpp
index e8e30a7e..7a816987 100644
--- a/src/frontend/qt_sdl/main.cpp
+++ b/src/frontend/qt_sdl/main.cpp
@@ -186,7 +186,8 @@ void audioMute()
         break;
 
     case 2: // only currently focused instance
-        if (!mainWindow->isActiveWindow()) audioMuted = true;
+        if (mainWindow != nullptr)
+            audioMuted = !mainWindow->isActiveWindow();
         break;
     }
 }