updaet SDK constraint for null safety (#27)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0997a12..2980e25 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+### 3.0.0-nullsafety.3
+
+* Update supported SDK range.
+
 ### 3.0.0-nullsafety.2
 
 * Update supported SDK range.
diff --git a/pubspec.yaml b/pubspec.yaml
index 1f761a5..4b5d08f 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,10 +1,10 @@
 name: platform
-version: 3.0.0-nullsafety.2
+version: 3.0.0-nullsafety.3
 description: A pluggable, mockable platform abstraction for Dart.
 homepage: https://github.com/google/platform.dart
 
+environment:
+  sdk: '>=2.10.0-0.0 <2.12.0'
+
 dev_dependencies:
   test: ^1.16.0-nullsafety.1
-
-environment:
-  sdk: '>=2.10.0-0.0 <2.11.0'