Enable strong mode
diff --git a/pubspec.yaml b/pubspec.yaml
index 7e79da2..51af26d 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -7,3 +7,5 @@
   sdk: '>=1.0.0 <2.0.0'
 dev_dependencies:
   test: ^0.12.0
+analyzer:
+  strong-mode: true