2.6.0 broke compatibility with npm 6

[kecskesk]

In my project the version 2.6.0 broke compatibility so I needed to reset to older versions, because of this error:
Invalid dependency type requested: alias

in these sub dependencies
4461 silly fetchPackageMetaData error for string-width-cjs@npm:string-width@^4.2.0 Invalid dependency type requested: alias
4462 silly fetchPackageMetaData error for strip-ansi-cjs@npm:strip-ansi@^6.0.1 Invalid dependency type requested: alias
4463 silly fetchPackageMetaData error for wrap-ansi-cjs@npm:wrap-ansi@^7.0.0 Invalid dependency type requested: alias

[TonyYoga]

Only npm >= 6.9.0 can handle aliases, plz check you npm versio