diff --git a/CHANGELOG.md b/CHANGELOG.md
index c690ee9..b6c30ae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 0.4.0
+
+- **BREAKING**: opt into null safety
+- feat!: upgrade Dart SDK constraints to `>=2.12.0-0 <3.0.0`
+
 # 0.4.0-nullsafety.0
 
 - **BREAKING**: opt into null safety
diff --git a/example/main.dart b/example/main.dart
index 0f0ff85..321c2c2 100644
--- a/example/main.dart
+++ b/example/main.dart
@@ -13,8 +13,8 @@ class NameInput extends FormzInput<String, NameInputError> {
 
   // Override validator to handle validating a given input value.
   @override
-  NameInputError? validator(String? value) {
-    return value?.isNotEmpty == true ? null : NameInputError.empty;
+  NameInputError? validator(String value) {
+    return value.isNotEmpty == true ? null : NameInputError.empty;
   }
 }
 
diff --git a/pubspec.yaml b/pubspec.yaml
index 340a66e..f9a143d 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -5,11 +5,11 @@ issue_tracker: https://github.com/ChicagoFlutter/formz/issues
 homepage: https://github.com/ChicagoFlutter/formz
 documentation: https://github.com/ChicagoFlutter/formz
 
-version: 0.4.0-nullsafety.0
+version: 0.4.0
 
 environment:
   sdk: ">=2.12.0-0 <3.0.0"
 
 dev_dependencies:
   coverage: ^0.14.2
-  test: ^1.16.0-nullsafety.9
+  test: ^1.16.0