diff --git a/package.json b/package.json
index 30d7726..ec68bcd 100644
--- a/package.json
+++ b/package.json
@@ -29,5 +29,9 @@
   },
   "homepage": "https://github.com/lscharen/iigs-game-engine#readme",
   "devDependencies": {
+    "pngjs": "^6.0.0",
+    "string-builder": "^0.1.8",
+    "watch": "latest",
+    "xml2json": "^0.12.0"
   }
 }