Open ipe with specific sheet from OS X command line

Hi,
I use a Macbook as laptop computer, and Ipe is one of my primary software 
packages. I use several different sheet styles, and on my desktop computer 
(Ubuntu), I can open a document specifying a stylesheet on the command line 
(ipe -sheet mysheet.isy). I can also open a document from the command line 
with ipe (ipe mydoc.pdf)

For some reason this does not work on my Macbook. It simply ignores 
everything after ipe (it basically opens a new basic document). I can open 
documents and load style sheets from the UI afterwards, without problems. 
This is not really a show-stopper, but it would be nice if I could use it the 
same way I use it on my Ubuntu box.

Any idea what the problem might be?

Thanks!

Cheerio,
WJ