diff --git a/packages/betterer/package.json b/packages/betterer/package.json
index db8b6fec..d2021fd0 100644
--- a/packages/betterer/package.json
+++ b/packages/betterer/package.json
@@ -36,6 +36,7 @@
     "@betterer/time": "^5.3.4",
     "@betterer/worker": "^5.3.4",
     "chokidar": "^3.6.0",
+    "core-js": "^3.38.1",
     "djb2a": "^2.0.0",
     "fast-memoize": "^2.5.2",
     "lines-and-columns": "^2.0.3",
diff --git a/packages/betterer/src/index.ts b/packages/betterer/src/index.ts
index adde8188..f53ab126 100644
--- a/packages/betterer/src/index.ts
+++ b/packages/betterer/src/index.ts
@@ -4,6 +4,8 @@
  * @packageDocumentation
  */
 
+import 'core-js/proposals/promise-with-resolvers.js';
+
 export type {
   BettererAPI,
   BettererOptions,