diff --git a/FSharpLu.Json/Compact.fs b/FSharpLu.Json/Compact.fs
index c521769..18b3c80 100644
--- a/FSharpLu.Json/Compact.fs
+++ b/FSharpLu.Json/Compact.fs
@@ -10,8 +10,18 @@ open Microsoft.FSharp.Reflection
type CompactUnionJsonConverter() =
inherit Newtonsoft.Json.JsonConverter()
+ let SomeFieldIdentifier = "Some"
+
let isOptionType (t:System.Type) =
- t.IsGenericType && t.GetGenericTypeDefinition() = typedefof