Persistent streams in an extension

I am trying to use a php_stream* as a global (and hence persistent) resource, but gdb detects a memory leak at the end of the request, and subsequent calls to the stream say the stream is no longer seekable. How do I declare a php_stream (opened presumably with php_stream_open_wrapper) to be a persistent resource, such that I will close it only on module shutdown? Cheers, Andrew.