diff --git a/CHANGELOG.md b/CHANGELOG.md
index b8601bc7..dc44d07d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # changelog
 
+ * 2.3.8 _unreleased_
+   * [reuse moduleid regexp](https://github.com/iambumblehead/esmock/pull/231) replacing separately created regexps
+   * [remove esmockIsLoader.js](https://github.com/iambumblehead/esmock/pull/231) export from esmockLoader.js instead
  * 2.3.7 _Aug.15.2023_
    * [normalize package.json url](https://github.com/iambumblehead/esmock/pull/225) and [reduce loc for loader verification](https://github.com/iambumblehead/esmock/pull/226)
    * [small adjustments](https://github.com/iambumblehead/esmock/pull/228) reducing lines of code
diff --git a/package.json b/package.json
index 43c92ee0..681aa532 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "esmock",
   "type": "module",
-  "version": "2.3.7",
+  "version": "2.3.8",
   "license": "ISC",
   "readmeFilename": "README.md",
   "description": "provides native ESM import and globals mocking for unit tests",
diff --git a/src/esmock.js b/src/esmock.js
index cb9ccbcd..5a3a1bd3 100644
--- a/src/esmock.js
+++ b/src/esmock.js
@@ -1,11 +1,11 @@
-import esmockIsLoader from './esmockIsLoader.js'
+import esmockLoader from './esmockLoader.js'
 import esmockModule from './esmockModule.js'
 import esmockArgs from './esmockArgs.js'
 import esmockErr from './esmockErr.js'
 
 const esmockGo = opts => async (...args) => {
   const [moduleId, parent, defs, gdefs, opt] = esmockArgs(args, opts)
-  if (!await esmockIsLoader())
+  if (!await esmockLoader())
     throw esmockErr.errMissingLoader()
 
   const fileURLKey = await esmockModule(moduleId, parent, defs, gdefs, opt)
diff --git a/src/esmockIsLoader.js b/src/esmockIsLoader.js
deleted file mode 100644
index c4175b03..00000000
--- a/src/esmockIsLoader.js
+++ /dev/null
@@ -1,3 +0,0 @@
-import { loaderIsVerified } from './esmockLoader.js'
-
-export default (c => () => (c = c || loaderIsVerified(import.meta.url)))()
diff --git a/src/esmockLoader.js b/src/esmockLoader.js
index d28f7aa0..6f60c391 100644
--- a/src/esmockLoader.js
+++ b/src/esmockLoader.js
@@ -19,6 +19,9 @@ const withHashRe = /.*#-#/
 const isesmRe = /isesm=true/
 const isnotfoundRe = /isfound=false/
 const hashbangRe = /^(#![^\n]*\n)/
+// returned regexp will match embedded moduleid w/ treeid
+const moduleIdReCreate = (moduleid, treeid) => new RegExp(
+  `.*(${moduleid}(\\?${treeid}(?:(?!#-#).)*)).*`)
 
 const globalPreload = (({ port }) => (
   port.addEventListener('message', ev => (
@@ -77,10 +80,9 @@ const resolve = async (specifier, context, nextResolve) => {
   const gdefs = url && url.replace(esmkgdefsAndBeforeRe, '')
   // do not call 'nextResolve' for notfound modules
   if (treeidspec.includes(`esmkModuleId=${specifier}&isfound=false`)) {
-    const moduleIdRe = new RegExp(
-      '.*file:///' + specifier + '(\\?' + treeid + '(?:(?!#-#).)*).*')
+    const moduleIdRe = moduleIdReCreate(`file:///${specifier}`, treeid)
     const moduleId = (
-      gdefs.match(moduleIdRe) || defs.match(moduleIdRe) || [])[1]
+      gdefs.match(moduleIdRe) || defs.match(moduleIdRe) || [])[2]
     if (moduleId) {
       return {
         shortCircuit: true,
@@ -97,8 +99,7 @@ const resolve = async (specifier, context, nextResolve) => {
   }
 
   const resolved = await nextResolveCall(nextResolve, specifier, context)
-  const moduleIdRe = new RegExp(
-    '.*(' + resolved.url + '\\?' + treeid + '(?:(?!#-#).)*).*')
+  const moduleIdRe = moduleIdReCreate(resolved.url, treeid)
   const moduleId =
     moduleIdRe.test(defs) && defs.replace(moduleIdRe, '$1') ||
     moduleIdRe.test(gdefs) && gdefs.replace(moduleIdRe, '$1')
@@ -118,11 +119,11 @@ const resolve = async (specifier, context, nextResolve) => {
   return resolved
 }
 
-const loaderVerificationQuery = '?esmock-loader=true'
-const loaderIsVerified = url => import(
-  url + loaderVerificationQuery).then(m => m.default === true)
+const loaderVerificationUrl = urlDummy + '?esmock-loader=true'
+const loaderIsVerified = (memo => () => memo = memo || (
+  import(loaderVerificationUrl).then(m => m.default === true)))()
 const load = async (url, context, nextLoad) => {
-  if (url.endsWith(loaderVerificationQuery)) {
+  if (url === loaderVerificationUrl) {
     return {
       format: 'module',
       shortCircuit: true,
@@ -187,4 +188,4 @@ 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, loaderIsVerified, globalPreload}
+export {load, resolve, getSource, globalPreload, loaderIsVerified as default}