diff --git a/config/tsconfig-build.json b/config/tsconfig-build.json
index 2f6f543d1a..4daa2fbade 100644
--- a/config/tsconfig-build.json
+++ b/config/tsconfig-build.json
@@ -1,8 +1,8 @@
 {
   "compilerOptions": {
     /* Basic Options */
-    "target": "ES5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
-    "module": "es2015",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
+    "target": "es2017",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
+    "module": "es2020",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
     // "lib": [],                             /* Specify library files to be included in the compilation. */
     "allowJs": true,                       /* Allow javascript files to be compiled. */
     // "checkJs": true,                       /* Report errors in .js files. */
@@ -58,7 +58,7 @@
     // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
   },
   "include": [
-    "../build/ol/src/**/*.js"
+    "../build/ol/**/*.js"
   ],
   "exclude": []
 }
\ No newline at end of file
diff --git a/package.json b/package.json
index 5c12c1b337..ecd263dd71 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,7 @@
     "build-site": "shx rm -rf build/site && npm run build-examples && npm run apidoc && npm run build-legacy && shx mkdir -p build/site && shx cp site/index.html build/site/ && shx mv build/apidoc build/examples build/legacy build/site/",
     "copy-css": "shx cp src/ol/ol.css build/ol/ol.css",
     "generate-types": "tsc --project config/tsconfig-build.json --declaration --declarationMap --emitDeclarationOnly --outdir build/ol",
-    "transpile": "shx rm -rf build/ol && shx mkdir -p build/ol && shx cp -rf src/ol build/ol/src && node tasks/serialize-workers.cjs && tsc --project config/tsconfig-build.json",
+    "transpile": "shx rm -rf build/ol && shx mkdir -p build/ol && shx cp -rf src/ol build && node tasks/serialize-workers.cjs",
     "typecheck": "tsc --pretty",
     "apidoc-debug": "shx rm -rf build/apidoc && node --inspect-brk=9229 ./node_modules/jsdoc/jsdoc.js -R config/jsdoc/api/index.md -c config/jsdoc/api/conf.json -P package.json -d build/apidoc",
     "apidoc": "shx rm -rf build/apidoc && jsdoc -R config/jsdoc/api/index.md -c config/jsdoc/api/conf.json -P package.json -d build/apidoc"
diff --git a/tasks/serialize-workers.cjs b/tasks/serialize-workers.cjs
index 757ea8a788..5ab7af7ffa 100644
--- a/tasks/serialize-workers.cjs
+++ b/tasks/serialize-workers.cjs
@@ -80,7 +80,7 @@ exports.build = build;
  */
 async function main() {
   const inputDir = path.join(__dirname, '../src/ol/worker');
-  const outputDir = path.join(__dirname, '../build/ol/src/worker');
+  const outputDir = path.join(__dirname, '../build/ol/worker');
 
   await fse.ensureDir(outputDir);