"Error: request argument is not a string" after upgrade to 5.0.x from 4.5.x

[0ptional]

Hey everyone!

I am in the process of upgrading some dependencies in our project. We have vue2 (2.7.14) and vue-cli (5.0.8). All vue-cli plugins are upgraded to the latest version, same with typescript and webpack plugins.

For some reason I am getting this error on some of my vue files:

Module not found: Error: request argument is not a string
./node_modules/@vue/cli-plugin-typescript/node_modules/babel-loader/lib/index.js!./node_modules/ts-loader/index.js??clonedRuleSet-41.use[1]!./node_modules/@vue/vue-loader-v15/lib/index.js??vue-loader-options!./src/components/SomeComponent.vue?vue&type=script&lang=ts& 20:0-65 216:4-15

To be honest, I don't even know what this error is trying to tell me and I couldn't find any reference to it in other issues. Any idea on what I should look for?

Thanks for any help.