no type error when using a default import

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import tsutils from 'tsutils' // no typescript error
tsutils.isTypeAliasDeclaration

at runtime:

tsutils_1.default.isTypeAliasDeclaration;
                  ^

TypeError: Cannot read properties of undefined (reading 'isTypeAliasDeclaration')

this seems to only be an issue with the compiled *.d.ts files, it doesn't happen with the source code. i'm not really sure how this project is built because npm run compile doesn't seem to output anything so it's difficult for me to minify the issue