diff --git a/tsconfig.json b/tsconfig.json
index 4063b5ae0..4350d90be 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -23,7 +23,8 @@
     "inlineSources": true,
     "strict": true,
     "strictNullChecks": false,
-    "target": "es2020",
+    "target": "es2018",
+    "lib": [ "es2020", "DOM", "DOM.Iterable" ],
     "types": ["lit", "jasmine"]
   },
   "exclude": [