diff --git a/optional_marshaljson.go b/optional_marshaljson.go
index 4d144cb..c2c8111 100644
--- a/optional_marshaljson.go
+++ b/optional_marshaljson.go
@@ -11,7 +11,7 @@ var _ json.Marshaler = Nothing[string]()
 // MarshalJSON makes it so json.Marshaler is implemented.
 func (receiver Optional[T]) MarshalJSON() ([]byte, error) {
 	switch interface{}(receiver.value).(type) {
-	case bool, string:
+	case bool, string, json.Marshaler:
 		// these are OK.
 	default:
 		return nil, fmt.Errorf("cannot marshal something of type %T into JSON because parameterized type is ‘%T’ rather than ‘bool’ or ‘string’", receiver, receiver.value)