vim-latexsuite syntax highlight in macro parameter

Question

I'm using vim with vim-latex to edit my LaTeX-files. I noticed that the \begin{env} and \end{env} are not colorized when they are in a macro parameter (the \vary command and question environment are part of the exsheets package):

\vary{
  \begin{question}
  \end{question}
}{
  \begin{question}
  \end{question}
}

I've attached a sample picture:

What should I do to colorize the \begin{question} inside \vary?

PS. I've asked it on tex.stackexchange but no answer.