diff --git a/SlidePresenter/GamepadReader/JoyConRead.cs b/SlidePresenter/GamepadReader/JoyConRead.cs
index f9b69fc..9459431 100644
--- a/SlidePresenter/GamepadReader/JoyConRead.cs
+++ b/SlidePresenter/GamepadReader/JoyConRead.cs
@@ -10,8 +10,8 @@ using wtf.cluster.JoyCon.InputReports;
 namespace ControllerSlidePresenter.GamepadReader;
 
 public class JoyConRead : IGamepadReader {
-	public event Action NextSlide;
-	public event Action PrevSlide;
+	public event Action? NextSlide;
+	public event Action? PrevSlide;
 
 	public async Task Read() {
 		Console.OutputEncoding = Encoding.UTF8;
diff --git a/SlidePresenter/GamepadReader/WiimoteRead.cs b/SlidePresenter/GamepadReader/WiimoteRead.cs
index 8f45454..5918a2e 100644
--- a/SlidePresenter/GamepadReader/WiimoteRead.cs
+++ b/SlidePresenter/GamepadReader/WiimoteRead.cs
@@ -4,8 +4,8 @@ using WiimoteLib.NetCore;
 namespace ControllerSlidePresenter.GamepadReader;
 
 public class WiimoteRead : IGamepadReader {
-	public event Action NextSlide;
-	public event Action PrevSlide;
+	public event Action? NextSlide;
+	public event Action? PrevSlide;
 
 	public async Task Read() {
 		Wiimote wiimote = new();
diff --git a/SlidePresenter/SlideSwitcher.cs b/SlidePresenter/SlideSwitcher.cs
index cd26bf0..3cd7c5d 100644
--- a/SlidePresenter/SlideSwitcher.cs
+++ b/SlidePresenter/SlideSwitcher.cs
@@ -16,11 +16,14 @@ public class SlideSwitcher : IDisposable {
 
 	public SlideSwitcher(IGamepadReader? reader) {
 		_reader = reader;
+		if (_reader == null) return;
+
 		_reader.NextSlide += NextSlide;
 		_reader.PrevSlide += PreviousSlide;
 	}
 
 	public void Dispose() {
+		if (_reader == null) return;
 		_reader.NextSlide -= NextSlide;
 		_reader.PrevSlide -= PreviousSlide;
 	}