💡 Update: This problem was discussed in webpack/webpack#6522. Setting output.globalObject to 'this' did the trick.

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Just a small test case, because it looks like I cannot create an UMD build with webpack, which can be required by Node.

Just run yarn && yarn build && yarn test.

I get this error:

ReferenceError: window is not defined
    at Object.<anonymous> (/mnt/c/Users/foo/webpack-umd-node/dist/main.js:1:272)

It looks like the UMD build expects window to be defined. AFAIK this shouldn't be the case.