Set min SDK to 2.7.0.
diff --git a/.travis.yml b/.travis.yml
index 04de0b4..1785982 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: dart
 
 dart:
-  - stable
+  - 2.7.0
   - dev
 
 dart_task:
diff --git a/pubspec.yaml b/pubspec.yaml
index c89986c..9d60ca7 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -7,7 +7,7 @@
 homepage: https://github.com/dart-lang/dart_style
 
 environment:
-  sdk: '>=2.3.0 <3.0.0'
+  sdk: '>=2.7.0 <3.0.0'
 
 dependencies:
   analyzer: ">=0.39.5 <0.40.0"