diff --git a/package.json b/package.json
index fbb946c1..d2684cd9 100644
--- a/package.json
+++ b/package.json
@@ -34,6 +34,7 @@
     "grunt-browserify": "^5.0.0",
     "grunt-contrib-concat": "^0.5.0",
     "grunt-contrib-watch": "^0.6.1",
+    "image-diff": "^1.6.3",
     "image-filter-core": "~1.0.0",
     "image-filter-threshold": "~1.0.0",
     "matchdep": "^0.3.0",