This is a (meanwhile) known regression with Rcpp 1.0.4, c.f. http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2020-March/010411.html
As a workaround you can install a fixed version from upstream's drat rpository, e.g.:
install.packages("Rcpp", repos="https://RcppCore.github.io/drat")