diff --git a/lib/src/undoable.dart b/lib/src/undoable.dart
index 888c3d9..85a0ef1 100644
--- a/lib/src/undoable.dart
+++ b/lib/src/undoable.dart
@@ -1,5 +1,6 @@
 class Undoable<T> {
-  Undoable(this._value, {Undoable<T>? previousValue}) : _previous = previousValue;
+  Undoable(this._value, {Undoable<T>? previousValue})
+      : _previous = previousValue;
 
   T _value;
   Undoable<T>? _previous;