diff --git a/package.json b/package.json
index e9c4a2d..f66996f 100644
--- a/package.json
+++ b/package.json
@@ -20,7 +20,7 @@
     "chai": "^4.1.1",
     "istanbul": "^0.4.1",
     "mocha": "^4.0.0",
-    "xo": "^0.20.0"
+    "xo": "^0.21.0"
   },
   "xo": {
     "esnext": true,