Unsupported conditional import of `dart:ui` found in flutter_cross|lib/ui.dart

I tried to run the example but web but got:

[SEVERE]build_web_compilers:entrypoint on web/main.dart (cached): Unable to find modules for some sources, this is usually the result of either a
bad import, a missing dependency in a package (or possibly a dev_dependency
needs to move to a real dependency), or a build failure (if importing a
generated file).

Please check the following imports:

`import 'package:flutter_cross/ui.dart';` from shared_ui|lib/home_page.dart at 2:1
[SEVERE]build_modules:module_library on package:flutter_cross/ui.dart (cached): Invalid argument(s): Unsupported conditional import of `dart:ui` found in flutter_cross|lib/ui.dart.

Any Idea?