Importing node module in ember-cli-build causing error in finding module `ember-resolver`

I'm trying to import an external dependency in my project by doing npm install --save-dev --registry=http://someDependency, and then use app.import('node_modules/someDependency') in ember-cli-build.js

But this is causing the following error:

Could not find module `ember-resolver` imported from `myapp/resolver`

All I have in myapp/resolver.js is:

import Resolver from 'ember-resolver';

export default Resolver;

Seems that it's looking for ember-resolver in myapp/resolver instead of node_module? But when I delete app.import('node_modules/someDependency') in ember-cli-build.js things are working fine.

Could someone give me some hint about what's going on here? Thanks a lot!

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ember version: 2.18.2

node version: 9.0.0

pm version: 5.5.1