diff --git a/optional_unmarshaljson.go b/optional_unmarshaljson.go
index 164fd4c..51e6a1c 100644
--- a/optional_unmarshaljson.go
+++ b/optional_unmarshaljson.go
@@ -10,11 +10,11 @@ var _ json.Unmarshaler = new(Optional[string])
 
 // UnmarshalJSON makes it so json.Unmarshaler is implemented.
 func (receiver *Optional[T]) UnmarshalJSON(data []byte) error {
-	switch interface{}(receiver.value).(type) {
-	case bool, string, json.Unmarshaler:
+	switch interface{}(&receiver.value).(type) {
+	case *bool, *string, json.Unmarshaler:
 		// these are OK.
 	default:
-		return fmt.Errorf("cannot unmarshal into something of type %T from JSON because parameterized type is ‘%T’ rather than ‘bool’, ‘string’, or ‘json.Unmarshaler’", receiver, receiver.value)
+		return fmt.Errorf("cannot unmarshal into something of type %T from JSON because pointer to parameterized type is ‘%T’ rather than ‘*bool’, ‘*string’, or ‘json.Unmarshaler’", receiver, &receiver.value)
 	}
 
 	{