diff --git a/FSharp.Json.Tests/AsJson.fs b/FSharp.Json.Tests/AsJson.fs
index 59feb9c..b88d350 100644
--- a/FSharp.Json.Tests/AsJson.fs
+++ b/FSharp.Json.Tests/AsJson.fs
@@ -54,3 +54,10 @@ module AsJson =
         let actual = Json.deserialize<AsJsonOptionalRecord> """{"value":null}"""
         let expected = { AsJsonOptionalRecord.value = None }
         Assert.AreEqual(expected, actual)
+
+    [<Test>]
+    let ``AsJson member deserialization untyped - null`` () =
+        let config = JsonConfig.create (jsonFieldNaming = Json.lowerCamelCase, allowUntyped = true )
+        let actual = Json.deserializeEx<obj list> config """[ {"value":null} ]"""
+        let expected = [ Map.ofList [ "value", None ] ]
+        Assert.AreEqual(expected[0], actual[0]) 
diff --git a/FSharp.Json/Core.fs b/FSharp.Json/Core.fs
index 6b7af4f..1b704d7 100644
--- a/FSharp.Json/Core.fs
+++ b/FSharp.Json/Core.fs
@@ -289,7 +289,7 @@ module internal Core =
         | JsonValue.Record _ -> typeof<Map<string, obj>>
         | JsonValue.Array _ -> getListType typeof<obj>
         | JsonValue.Boolean _ -> typeof<bool>
-        | _ -> null
+        | _ -> typeof<unit>
                 
     let rec deserialize (config: JsonConfig) (path: JsonPath) (t: Type) (jvalue: JsonValue): obj =
         let deserializeEnum (path: JsonPath) (t: Type) (jsonField: JsonField) (jvalue: JsonValue): obj =
@@ -368,6 +368,8 @@ module internal Core =
                         JsonValueHelpers.getDateTimeOffset CultureInfo.InvariantCulture path jvalue :> obj
                     | t when t = typeof<Guid> ->
                         JsonValueHelpers.getGuid path jvalue :> obj
+                    | t when t = typeof<unit> ->
+                        None :> obj
                     | t when t.IsEnum ->
                         deserializeEnum path t jsonField jvalue
                     | t when isTuple t || isList t || isArray t || isMap t || isRecord t || isUnion t ->