lua_load modifies the stack

[Marc Balmer <marc@...>]

I have a table on the stack, then I call lua_load() to load a function.
 After lua_load() completes without an error, I have a function on top
of the stack.  But my table, which should now be at position -2, is
gone.  There is a nil value there.

Hwo can that happen?  Is that some memory corruption in my lua_Reader
function or are there situations where lua_load() modifies the stack in
such a way?