# \tableofcontents inside breakable tcolorbox

I want to put the toc (with \tableofcontents) of a larger document (with a lot of \includes, so I do not know how to make a simple example out of it) into a breakable tcolorbox. The toc is correct, the box appears but I get always at fist two pages with an empty broken box (containing only 1 empty line) and the toc starts at the 3rd page, where the title now sticks near the top of the box. The "lines before break" option has no affect at all. Is there anybody who knows, how to avoid the empty pages? Thanks in advance,

Thomas.