If the variable $font-weight-normal is set to a non-default value, e.g. "300", this value is not inherited by text inputs. The computed value of the font-weight property is found to be 'reset' to 400 in the developer tools (Firefox 62.0). When you add 'font-weight: inherit;' to the text input, this is solved. Another solution could be to add a $input-font-weight variable.