diff --git a/Xamarin.Essentials/Share/Share.ios.cs b/Xamarin.Essentials/Share/Share.ios.cs
index 8f44b6333..48fb31278 100644
--- a/Xamarin.Essentials/Share/Share.ios.cs
+++ b/Xamarin.Essentials/Share/Share.ios.cs
@@ -57,8 +57,8 @@ static Task PlatformRequestAsync(ShareFileRequest request)
 
     class ShareActivityItemSource : UIActivityItemSource
     {
-        NSObject item;
-        string subject;
+        readonly NSObject item;
+        readonly string subject;
 
         internal ShareActivityItemSource(NSObject item, string subject)
         {