diff --git a/build.js b/build.js
index 8cccff7..0ce633a 100755
--- a/build.js
+++ b/build.js
@@ -8,6 +8,8 @@ const entryPoints = fs
     file =>
       file.endsWith('.ts') &&
       file !== 'core.ts' &&
+      file !== 'test-helpers.ts' &&
+      file !== 'helpers.ts' &&
       !file.endsWith('.test.ts') &&
       fs.statSync(join(process.cwd(), file)).isFile(),
   )
diff --git a/helpers.ts b/helpers.ts
new file mode 100644
index 0000000..9931320
--- /dev/null
+++ b/helpers.ts
@@ -0,0 +1,9 @@
+export async function yieldThread() {
+  return new Promise(resolve => {
+    const ch = new MessageChannel()
+    // @ts-ignore (typescript thinks this property should be called `addListener`, but in fact it's `addEventListener`)
+    ch.port1.addEventListener('message', resolve)
+    ch.port2.postMessage(0)
+    ch.port1.start()
+  })
+}
diff --git a/relay.ts b/relay.ts
index e86e5e6..d7e3c33 100644
--- a/relay.ts
+++ b/relay.ts
@@ -5,6 +5,7 @@ import { matchFilters, type Filter } from './filter.ts'
 import { getHex64, getSubscriptionId } from './fakejson.ts'
 import { Queue, normalizeURL } from './utils.ts'
 import { nip42 } from './index.ts'
+import { yieldThread } from './helpers.ts'
 
 export function relayConnect(url: string) {
   const relay = new Relay(url)
@@ -12,15 +13,6 @@ export function relayConnect(url: string) {
   return relay
 }
 
-async function yieldThread() {
-  return new Promise((resolve) => {
-    const ch = new MessageChannel();
-    ch.port1.addEventListener('message', () => resolve());
-    ch.port2.postMessage(0);
-    ch.port1.start();
-  });
-}
-
 export class Relay {
   public readonly url: string
   private _connected: boolean = false