ctable and siunitx: Last column does not center correctly (possible incompatibility?)

Question

I would like to use ctable in my thesis for tables and graphics and I also would like to use siunitx for formatting numbers and aligning numbers on the decimal marker in tables.

Everything seemed to work well until I discovered some strange behaviour in the last column. The heading does not get centered there (I tried the different settings for siunitx: table-alignment, table-text-alignment, in the preamble and for the specific column). It did not help.

ctable version is rev 26694, v 1.23;

siunitx is rev 29017, v 2.5p

This is my minimal example:

\documentclass[english]{book}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{ctable}
\usepackage{siunitx}
\begin{document}

% Does not center the heading in the last column.
\ctable[]{
  |l
  |S
  |S
  |S|
}{}{
  \FL
  &         {Tom} &     {Suzy} &    {Rob} \ML
  Eating &      122.5 &     1.025 &     1.5 \NN
  Sleeping &    9.1 &       1346.5 &    213.7 \NN
  Working &     7.5 &       9.5 &       2.0125 \NN
  Watching TV & 5.25 &      117.5 &     7.5 \LL}

% Works fine with simple tabular
\begin{tabular}{
  |l
  |S
  |S
  |S|
  }
  \hline
  &         {Tom} &     {Suzy} &    {Rob} \\ \hline
  Eating &      122.5 &     1.025 &     1.5 \\
  Sleeping &    9.1 &       1346.5 &    213.7 \\
  Working &     7.5 &       9.5 &       2.0125 \\
  Watching TV & 5.25 &      117.5 &     7.5 \\ \hline
\end{tabular}

\end{document}

This is how it looks to me:

Answer 1

Just to close off the solution in the comments

Rather than change the preamble you can just change \ML to \tabularnewline \midrule which is the same thing, but works.