Incompatible units in _modal.scss

[jbgh2]

I followed the installation instructions and when I ran gulp serve I got this error message:

Details: status: 1 file: /Stellar/node_modules/bootstrap/scss/_modal.scss line: 177 column: 12 formatted: Error: Incompatible units: 'rem' and 'px'. on line 177 of node_modules/bootstrap/scss/_modal.scss from line 38 of node_modules/bootstrap/scss/bootstrap.scss from line 121 of scss/style.scss

padding: $modal-inner-padding - $modal-footer-margin-between / 2;

-----------^

messageFormatted: node_modules\bootstrap\scss\_modal.scss

Error: Incompatible units: 'rem' and 'px'. on line 177 of node_modules/bootstrap/scss/_modal.scss from line 38 of node_modules/bootstrap/scss/bootstrap.scss from line 121 of scss/style.scss

padding: $modal-inner-padding - $modal-footer-margin-between / 2;

-----------^

messageOriginal: Incompatible units: 'rem' and 'px'.
relativePath: node_modules\bootstrap\scss\_modal.scss

I'm using Windows 10. Node: 12.14.1 NPM: 6.13.4 Gulp: CLI: 2.2.0, Local: 4.0.2