update minimum supported SDK
diff --git a/pkgs/coverage/pubspec.yaml b/pkgs/coverage/pubspec.yaml
index 3f9bdc2..58b906b 100644
--- a/pkgs/coverage/pubspec.yaml
+++ b/pkgs/coverage/pubspec.yaml
@@ -4,7 +4,7 @@
 description: Coverage data manipulation and formatting
 homepage: https://github.com/dart-lang/coverage
 environment:
-  sdk: '>=1.9.0 <2.0.0'
+  sdk: '>=1.12.0 <2.0.0'
 dependencies:
   args: '>=0.12.1 <1.0.0'
   logging: '>=0.9.0 <0.12.0'