diff --git a/csharp/src/Google.Protobuf/WritingPrimitives.cs b/csharp/src/Google.Protobuf/WritingPrimitives.cs
index 1a25f8e9d3bf..dccf2429a72f 100644
--- a/csharp/src/Google.Protobuf/WritingPrimitives.cs
+++ b/csharp/src/Google.Protobuf/WritingPrimitives.cs
@@ -46,11 +46,8 @@ namespace Google.Protobuf
     [SecuritySafeCritical]
     internal static class WritingPrimitives
     {
-#if NET5_0
-        internal static Encoding Utf8Encoding => Encoding.UTF8; // allows JIT to devirtualize
-#else
-        internal static Encoding Utf8Encoding = Encoding.UTF8; // "Local" copy of Encoding.UTF8, for efficiency. (Yes, it makes a difference.)
-#endif
+        // "Local" copy of Encoding.UTF8, for efficiency. (Yes, it makes a difference.)
+        internal static readonly Encoding Utf8Encoding = Encoding.UTF8;
 
         #region Writing of values (not including tags)