Adding this here, since this comes up in search results and the answers provided here didn’t work for me.
What worked for me was using ng update @angular/core@7.0.0. This should probably be noted in the Angular Update Guide (https://update.angular.io/), but it’s not. Since that page throws a notice up when upgrading across more than one major version at a time, but using the recommended command ng update @angular/core upgrades to the latest release (which could be across more than one major version), perhaps this should be changed.