diff --git a/packages/x-charts-vendor/es/d3-array.js b/packages/x-charts-vendor/es/d3-array.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-array.js
rename to packages/x-charts-vendor/es/d3-array.mjs
diff --git a/packages/x-charts-vendor/es/d3-color.js b/packages/x-charts-vendor/es/d3-color.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-color.js
rename to packages/x-charts-vendor/es/d3-color.mjs
diff --git a/packages/x-charts-vendor/es/d3-delaunay.js b/packages/x-charts-vendor/es/d3-delaunay.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-delaunay.js
rename to packages/x-charts-vendor/es/d3-delaunay.mjs
diff --git a/packages/x-charts-vendor/es/d3-format.js b/packages/x-charts-vendor/es/d3-format.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-format.js
rename to packages/x-charts-vendor/es/d3-format.mjs
diff --git a/packages/x-charts-vendor/es/d3-interpolate.js b/packages/x-charts-vendor/es/d3-interpolate.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-interpolate.js
rename to packages/x-charts-vendor/es/d3-interpolate.mjs
diff --git a/packages/x-charts-vendor/es/d3-path.js b/packages/x-charts-vendor/es/d3-path.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-path.js
rename to packages/x-charts-vendor/es/d3-path.mjs
diff --git a/packages/x-charts-vendor/es/d3-scale.js b/packages/x-charts-vendor/es/d3-scale.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-scale.js
rename to packages/x-charts-vendor/es/d3-scale.mjs
diff --git a/packages/x-charts-vendor/es/d3-shape.js b/packages/x-charts-vendor/es/d3-shape.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-shape.js
rename to packages/x-charts-vendor/es/d3-shape.mjs
diff --git a/packages/x-charts-vendor/es/d3-time-format.js b/packages/x-charts-vendor/es/d3-time-format.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-time-format.js
rename to packages/x-charts-vendor/es/d3-time-format.mjs
diff --git a/packages/x-charts-vendor/es/d3-time.js b/packages/x-charts-vendor/es/d3-time.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/d3-time.js
rename to packages/x-charts-vendor/es/d3-time.mjs
diff --git a/packages/x-charts-vendor/es/delaunator.js b/packages/x-charts-vendor/es/delaunator.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/delaunator.js
rename to packages/x-charts-vendor/es/delaunator.mjs
diff --git a/packages/x-charts-vendor/es/internmap.js b/packages/x-charts-vendor/es/internmap.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/internmap.js
rename to packages/x-charts-vendor/es/internmap.mjs
diff --git a/packages/x-charts-vendor/es/robust-predicates.js b/packages/x-charts-vendor/es/robust-predicates.mjs
similarity index 100%
rename from packages/x-charts-vendor/es/robust-predicates.js
rename to packages/x-charts-vendor/es/robust-predicates.mjs
diff --git a/packages/x-charts-vendor/scripts/build.js b/packages/x-charts-vendor/scripts/build.js
index 169e75aee51c..ff634f2fbac3 100644
--- a/packages/x-charts-vendor/scripts/build.js
+++ b/packages/x-charts-vendor/scripts/build.js
@@ -118,7 +118,7 @@ const main = async () => {
 
     // Create library indexes and copy licenses to `lib-vendor.
     await Promise.all([
-      fs.writeFile(path.join(EsmBasePath, `${pkgName}.js`), getEsmIndex(pkg)),
+      fs.writeFile(path.join(EsmBasePath, `${pkgName}.mjs`), getEsmIndex(pkg)),
       fs.writeFile(path.join(CjsBasePath, `${pkgName}.js`), getCjsIndex(pkg)),
       fs
         .copyFile(path.join(pkgBase, 'LICENSE'), path.join(libVendorPath, 'LICENSE'))