diff --git a/src/NmeaParser/NmeaDevice.cs b/src/NmeaParser/NmeaDevice.cs
index accb039..2ac3d98 100644
--- a/src/NmeaParser/NmeaDevice.cs
+++ b/src/NmeaParser/NmeaDevice.cs
@@ -223,7 +223,7 @@ namespace NmeaParser
 		/// <summary>
 		/// Occurs when an NMEA message is received.
 		/// </summary>
-		public event EventHandler<NmeaMessageReceivedEventArgs> MessageReceived;
+		public event EventHandler<NmeaMessageReceivedEventArgs>? MessageReceived;
 
 		/// <summary>
 		/// Releases unmanaged and - optionally - managed resources.
diff --git a/src/NmeaParser/SystemNmeaDevice.Android.cs b/src/NmeaParser/SystemNmeaDevice.Android.cs
index 7cbc380..37d9b11 100644
--- a/src/NmeaParser/SystemNmeaDevice.Android.cs
+++ b/src/NmeaParser/SystemNmeaDevice.Android.cs
@@ -104,7 +104,7 @@ namespace NmeaParser
                 NmeaMessage?.Invoke(this, message);
             }
 
-            public event EventHandler<string> NmeaMessage;
+            public event EventHandler<string>? NmeaMessage;
 
             public float Accuracy = float.NaN;