Correction to: Nature https://doi.org/10.1038/s41586-019-1484-9, published online 15 August 2019.

In this Letter, the first name of author Staffan Holmqvist was misspelled as ‘Steffan’. In addition, the funding statement in the Acknowledgements section should have mentioned that the work was supported by a Royal Society University Research Fellowship (to K.J.C.). The Letter has been corrected online.