Update minimum SDK
diff --git a/.travis.yml b/.travis.yml
index b202aac..bf601a1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@
 dart:
   - dev
   - stable
-  - 1.22.0
+  - 1.23.0
 
 dart_task:
   - test: --platform vm
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 63cf006..fbf12f2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 * Update to make the code work with strong-mode clean Zone API.
 
+* Required minimum SDK of 1.23.0.
+
 ## 1.3.1
 
 * Fix the type annotation of `Pool.withResource()` to indicate that it takes
diff --git a/pubspec.yaml b/pubspec.yaml
index 4a8271b..3c65826 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -7,7 +7,7 @@
   async: "^1.4.0"
   stack_trace: ">=0.9.2 <2.0.0"
 environment:
-  sdk: ">=1.22.0 <2.0.0"
+  sdk: ">=1.23.0 <2.0.0"
 dev_dependencies:
   fake_async: ">=0.1.0 <0.2.0"
   test: ">=0.12.0 <0.13.0"