LaTeX: cite with [ ] argument in caption -

i need source of images listed in "list of figures". want cite inside caption argument:

this works:

\caption[plan,\protect\cite{damluji1992}]{plan} 

this works need in caption argument in next example:

\cite[p.156]{damluji1992} 

i need doesn't work:

\caption[plan,\protect\cite[p.156]{damluji1992}]{plan} 

it gives me error "argument of \har@dcite has }." in *.lof file corresponding line looks this:

\contentsline {figure}{\numberline {2}{\ignorespaces plan, \cite [s.156}}{5}{figure.caption.4} 

-> cite argument in { } missing!

without cite argument in [ ] looks this:

\contentsline {figure}{\numberline {2}{\ignorespaces plan, \cite {damluji1992}}}{5}{figure.caption.4} 

i stumbled on page same question , found answer @ http://www.latex-community.org/forum/viewtopic.php?f=50&t=6225

the solution: put curly braces around cite command:

{\cite[theorem~2]{metal}} 

the reason necessary have optional [] argument inside optional [] argument.