Prepare to publish stable null safety (#153)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2d99c3..d43d717 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.5.0
+
+* Stable release for null safety.
+
 ## 2.5.0-nullsafety.3
 
 * Update SDK constraints to `>=2.12.0-0 <3.0.0` based on beta release
diff --git a/pubspec.yaml b/pubspec.yaml
index 3aa8080..3c8dd95 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: async
-version: 2.5.0-nullsafety.3
+version: 2.5.0
 
 description: Utility functions and classes related to the 'dart:async' library.
 homepage: https://www.github.com/dart-lang/async
@@ -8,7 +8,7 @@
   sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
-  collection: '>=1.15.0-nullsafety <1.15.0'
+  collection: ^1.15.0
 
 dev_dependencies:
   fake_async: ^1.2.0-nullsafety