Angular 13 adds type="module" to the .js script tags in index.html

I have two very similar apps, one in Angular 12 CLI and the other in Angular 13. The newer one adds type="module" to the script tags for the generated .js files, which gives MIME errors in AppEngine under chrome. If I remove 'type="module"' from dist/index.html by hand, it runs no problem. I have checked, and there is no substantive difference in tsconfig*.json nor package.json, nor angular.json, nor the source index.html. Anywhere else to look?