diff --git a/pubspec.yaml b/pubspec.yaml
index 0b56c01..a358e43 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -4,7 +4,7 @@ version: 1.0.0
 # homepage: https://www.example.com
 
 environment:
-  sdk: '>=2.18.6 <3.0.0'
+  sdk: '<4.0.0'
 
 dependencies:
   json_annotation: ^4.8.0