diff --git a/config/webpack-config-legacy-build.js b/config/webpack-config-legacy-build.mjs
similarity index 100%
rename from config/webpack-config-legacy-build.js
rename to config/webpack-config-legacy-build.mjs
diff --git a/examples/webpack/config.js b/examples/webpack/config.mjs
similarity index 100%
rename from examples/webpack/config.js
rename to examples/webpack/config.mjs
diff --git a/package.json b/package.json
index 28cc6787d8..29db354dab 100644
--- a/package.json
+++ b/package.json
@@ -18,11 +18,11 @@
     "test": "npm run test-browser && npm run test-node && npm run test-rendering -- --force",
     "karma": "karma start test/browser/karma.config.cjs",
     "start": "npm run serve-examples",
-    "serve-examples": "webpack serve --config examples/webpack/config.js --mode development",
-    "build-examples": "webpack --config examples/webpack/config.js --mode production",
+    "serve-examples": "webpack serve --config examples/webpack/config.mjs --mode development",
+    "build-examples": "webpack --config examples/webpack/config.mjs --mode production",
     "build-package": "npm run transpile && npm run copy-css && npm run generate-types && node tasks/prepare-package.js",
     "build-index": "shx rm -f build/index.js && npm run build-package && node tasks/generate-index.js",
-    "build-legacy": "shx rm -rf build/legacy && npm run build-index && webpack --config config/webpack-config-legacy-build.js && cleancss --source-map src/ol/ol.css -o build/legacy/ol.css",
+    "build-legacy": "shx rm -rf build/legacy && npm run build-index && webpack --config config/webpack-config-legacy-build.mjs && cleancss --source-map src/ol/ol.css -o build/legacy/ol.css",
     "build-site": "npm run build-examples && npm run apidoc && mkdir -p build/site && cp site/index.html build/site && mv build/apidoc build/site/apidoc && mv build/examples build/site/examples",
     "copy-css": "shx cp src/ol/ol.css build/ol/ol.css",
     "generate-types": "npx --package=typescript@3.8.3 -y -- tsc --project config/tsconfig-build.json --declaration --declarationMap --emitDeclarationOnly --outdir build/ol",