diff --git a/src/esmockCache.js b/src/esmockCache.js
index 51c625b6..6e5e535b 100644
--- a/src/esmockCache.js
+++ b/src/esmockCache.js
@@ -1,3 +1,5 @@
+import esmockPostMessage from './esmockRegister.js'
+
 const esmockCache = {
   isESM: {},
 
@@ -7,8 +9,7 @@ const esmockCache = {
 }
 
 const esmockTreeIdSet = (key, keylong) => (
-  typeof global.postMessageEsmk === 'function'
-    && global.postMessageEsmk({ key, keylong }),
+  esmockPostMessage({ key, keylong }),
   global.mockKeys[String(key)] = keylong)
 
 const esmockTreeIdGet = key => (
diff --git a/src/esmockLoader.js b/src/esmockLoader.js
index b5f0024e..9245b4ce 100644
--- a/src/esmockLoader.js
+++ b/src/esmockLoader.js
@@ -1,6 +1,7 @@
 import fs from 'node:fs/promises'
 import process from 'process'
 import esmockErr from './esmockErr.js'
+// import './esmockCache.js'
 
 const [major, minor] = process.versions.node.split('.').map(it => +it)
 const isLT1612 = major < 16 || (major === 16 && minor < 12)
@@ -28,13 +29,26 @@ const hashbangRe = /^(#![^\n]*\n)/
 const moduleIdReCreate = (moduleid, treeid) => new RegExp(
   `.*(${moduleid}(\\?${treeid}(?:(?!#-#).)*)).*`)
 
+// node v12.0-v18.x, global
+const mockKeys = global.mockKeys || {}
+
+// node v20.0-v20.6
 const globalPreload = (({ port }) => (
   port.addEventListener('message', ev => (
-    global.mockKeys[ev.data.key] = ev.data.keylong)),
+    mockKeys[ev.data.key] = ev.data.keylong)),
   port.unref(),
   'global.postMessageEsmk = d => port.postMessage(d)'
 ))
 
+// node v20.6-current
+const initialize = data => {
+  if (data && data.port) {
+    data.port.on('message', msg => {
+      mockKeys[msg.key] = msg.keylong
+    })
+  }
+}
+
 const parseImports = defstr => {
   const [specifier, imports] = (defstr.match(esmkImportRe) || [])
 
@@ -57,7 +71,7 @@ const parseImportsTree = treeidspec => {
 }
 
 const treeidspecFromUrl = url => esmkIdRe.test(url)
-  && global.esmockTreeIdGet(url.match(esmkIdRe)[0].split('=')[1])
+  && mockKeys[url.match(esmkIdRe)[0].split('=')[1]]
 
 // new versions of node: when multiple loaders are used and context
 // is passed to nextResolve, the process crashes in a recursive call
@@ -201,4 +215,11 @@ const load = async (url, context, nextLoad) => {
 // node lt 16.12 require getSource, node gte 16.12 warn remove getSource
 const getSource = isLT1612 && load
 
-export {load, resolve, getSource, globalPreload, loaderIsVerified as default}
+export {
+  load,
+  resolve,
+  getSource,
+  initialize,
+  globalPreload,
+  loaderIsVerified as default
+}
diff --git a/src/esmockRegister.js b/src/esmockRegister.js
new file mode 100644
index 00000000..fdbcf5cc
--- /dev/null
+++ b/src/esmockRegister.js
@@ -0,0 +1,17 @@
+import { register } from 'node:module'
+import { MessageChannel } from 'node:worker_threads'
+
+const { port2, port1 } = new MessageChannel()
+
+register('./esmockLoader.js', {
+  parentURL: import.meta.url,
+  data: { port: port2 },
+  transferList: [port2]
+})
+
+export default msg => {
+  if (typeof global.postMessageEsmk === 'function')
+    global.postMessageEsmk(msg)
+  if (port1)
+    port1.postMessage(msg)
+}
diff --git a/tests/tests-node/package.json b/tests/tests-node/package.json
index a75d8ae8..f79a3f70 100644
--- a/tests/tests-node/package.json
+++ b/tests/tests-node/package.json
@@ -15,6 +15,7 @@
   "scripts": {
     "test:metaresolve": "node --experimental-import-meta-resolve --loader=esmock --test",
     "test": "node --loader=esmock --test && npm run test:metaresolve",
-    "test-one": "node --loader=esmock --test"
+    "test-one": "node --loader=esmock --test",
+    "test-one-no--loader": "node --test"
   }
 }