diff --git a/build/tasks/esbuild.js b/build/tasks/esbuild.js
index 30dbeb4e..ad074a52 100644
--- a/build/tasks/esbuild.js
+++ b/build/tasks/esbuild.js
@@ -23,6 +23,7 @@ module.exports = function (grunt) {
             entryPoints: [entry],
             outfile: path.join(dest, name),
             minify: false,
+            format: 'esm',
             bundle: true
           })
             .then(done)