diff --git a/package.json b/package.json
index 47f7bf0..34ecd76 100644
--- a/package.json
+++ b/package.json
@@ -7,8 +7,13 @@
   "author": "Andrew Kemp",
   "license": "MIT",
   "scripts": {
-    "test": "jest"
+    "test": "jest",
+    "test:debug": "jest test --runInBand --verbose=false"
   },
+  "engines" : {
+    "node" : "> 12.16.0",
+    "yarn": "> 1.22.0"
+  }, 
   "dependencies": {
     "reflect-metadata": "^0.1.13",
     "tslib": "^1.11.1",
diff --git a/tsconfig.json b/tsconfig.json
index e69dd7c..ee07516 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -18,6 +18,7 @@
       ],
       "lib": [
         "es2017",
+        "ES2019",
         "dom"
       ]
   },