diff --git a/pubspec.yaml b/pubspec.yaml
index 560fc15..9f6e842 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -4,7 +4,7 @@ repository: https://github.com/w2sv/koala
 version: 0.1.4
 
 environment:
-  sdk: '>=2.13.0 <=3.3.1'
+  sdk: '<=3.3.3'
 
 dependencies:
   collection: ^1.16.0