diff --git a/packages/angular_devkit/build_angular/src/angular-cli-files/models/webpack-configs/common.ts b/packages/angular_devkit/build_angular/src/angular-cli-files/models/webpack-configs/common.ts
index d34b783cf9..76b4709277 100644
--- a/packages/angular_devkit/build_angular/src/angular-cli-files/models/webpack-configs/common.ts
+++ b/packages/angular_devkit/build_angular/src/angular-cli-files/models/webpack-configs/common.ts
@@ -237,7 +237,7 @@ export function getCommonConfig(wco: WebpackConfigOptions) {
     mode: buildOptions.optimization ? 'production' : 'development',
     devtool: false,
     resolve: {
-      extensions: ['.ts', '.js'],
+      extensions: ['.ts', '.mjs', '.js'],
       symlinks: !buildOptions.preserveSymlinks,
       modules: [
         wco.tsConfig.options.baseUrl || projectRoot,