diff --git a/src/Avalonia.X11/X11Platform.cs b/src/Avalonia.X11/X11Platform.cs
index a2bd57404b..8ff3b4f5e0 100644
--- a/src/Avalonia.X11/X11Platform.cs
+++ b/src/Avalonia.X11/X11Platform.cs
@@ -105,7 +105,7 @@ namespace Avalonia.X11
         public IntPtr DeferredDisplay { get; set; }
         public IntPtr Display { get; set; }
 
-        private static uint[] X11IconConverter(IWindowIconImpl? icon)
+        private static uint[] X11IconConverter(IWindowIconImpl icon)
         {
             if (!(icon is X11IconData x11icon))
                 return Array.Empty<uint>();