diff --git a/pkgs/build-support/node/fetch-yarn-deps/index.js b/pkgs/build-support/node/fetch-yarn-deps/index.js
index 400b64d2e920..6bcc70837138 100755
--- a/pkgs/build-support/node/fetch-yarn-deps/index.js
+++ b/pkgs/build-support/node/fetch-yarn-deps/index.js
@@ -141,10 +141,20 @@ const performParallel = tasks => {
 	return Promise.all(workers)
 }
 
+// This could be implemented using [`Map.groupBy`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/groupBy),
+// but that method is only supported starting with Node 21
+const uniqueBy = (arr, callback) => {
+	const map = new Map()
+	for (const elem of arr) {
+		map.set(callback(elem), elem)
+	}
+	return [...map.values()]
+}
+
 const prefetchYarnDeps = async (lockContents, verbose) => {
 	const lockData = lockfile.parse(lockContents)
 	await performParallel(
-		Object.entries(lockData.object)
+		uniqueBy(Object.entries(lockData.object), ([_, value]) => value.resolved)
 		.map(([key, value]) => () => downloadPkg({ key, ...value }, verbose))
 	)
 	await fs.promises.writeFile('yarn.lock', lockContents)