How can I use normalize isotopic ratios from a single study using CIAAWconsensus package

Question

I want to use the package CIAAWconsensus by Juris Meija and Antonio Possolo, to normalize the isotopic ratios of the NIST SRM 981 to the reference isotope 207Pb. I get an error that I can not understand when I use the function normalize ratios:

library(CIAAWconsensus)
## Certified isotopic ratios in NIST SRM 981 (Value, standard uncertainty)
CertiRati.SRM.981 <- list(R.204.206 = c(0.059042, 0.000037/2),
                          R.207.206 = c(0.91464,  0.00033/2),
                          R.208.206 = c(2.1681,  0.0008/2))

## Ordering the data frame as requested by package
(dat <- data.frame(Study = 1:3, Year = rep(1991, 3), Author = rep('NIST', 3),
                   Outcome = c('204Pb/206Pb', '207Pb/206Pb', '208Pb/206Pb'),
                   Value = c(CertiRati.SRM.981[[1]][1],
                             CertiRati.SRM.981[[2]][1], 
                             CertiRati.SRM.981[[3]][1]),
                   Unc = c(CertiRati.SRM.981[[1]][2],
                           CertiRati.SRM.981[[2]][2], 
                           CertiRati.SRM.981[[3]][2]),
                   k_extra = rep(1, 3)))

#   Study Year Author     Outcome    Value      Unc k_extra
# 1     1 1991   NIST 204Pb/206Pb 0.059042 1.85e-05       1
# 2     2 1991   NIST 207Pb/206Pb 0.914640 1.65e-04       1
# 3     3 1991   NIST 208Pb/206Pb 2.168100 4.00e-04       1

## Atempt to normalize the ratios to the 207Pb
normalize.ratios(dat = dat, element = 'lead', ref.isotope = '207Pb')

# Error in dimnames(x) <- dn :
#    Length of 'dimnames' [2] not equal to array extent

The dataframe is created as indicated in the package's documentation but can not get around this. Any help will be much appreciated.