update sdk constraint
diff --git a/pubspec.yaml b/pubspec.yaml
index 935a919..958487e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -5,4 +5,4 @@
 homepage: https://github.com/dart-lang/pedantic
 
 environment:
-  sdk: '>=2.9.0-1 <2.9.0'
+  sdk: '>=2.9.0-18.0 <2.9.0'