How to create more than OPEN_MAX message mqueues ?

My project include many child process, and they communicate each other
by message.
This works well before ,but now I want to increase a new process ,and
the total message mqueues has up to 16 , so when the new process create a
message mqueue, the mq_open function return a error — “Too many open files
in system”.
Could anybody help me to create more than OPEN_MAX message mqueues ?
Thanks