diff --git a/index.js b/index.js
index 664db39..20902da 100644
--- a/index.js
+++ b/index.js
@@ -31,6 +31,7 @@ module.exports = {
         'space-in-parens': ['error', 'never'],
         'space-infix-ops': 'error',
         'space-unary-ops': 'error',
+        'strict': ['error', 'global'],
         'no-only-tests/no-only-tests': 'error'
     }
 };