No results obtained if interating a second time on the same cursor with a limit

[shnups]

This code snippet:

import logging

from appnexus import Campaign, connect

connect('XXXXXXXXXX', 'XXXXXXXXXX')

def gather(cursor):
    print("----------")
    print("Cursor.before:\tskip={}, limit={}, len={}, size={}" \
        .format(cursor._skip, cursor._limit, len(cursor), cursor.size()))

    results = [res for res in cursor]   

    print("Results ({}):\t{}".format(len(results), ','.join([str(r.id) for r in results])))
    print("Cursor.after:\tskip={}, limit={}, len={}, size={}" \
        .format(cursor._skip, cursor._limit, len(cursor), cursor.size()))

cursor = Campaign.find(advertiser_id=XXXXXXXXXX)
cursor.limit(50)
gather(cursor)
gather(cursor)

will output the following:

----------
Cursor.before:  skip=0, limit=50, len=228, size=50
Results (50):   XXXXXXXXXX, XXXXXXXXXX,...(redacted)...,XXXXXXXXXX,XXXXXXXXXX
Cursor.after:   skip=0, limit=50, len=228, size=50
----------
Cursor.before:  skip=0, limit=50, len=228, size=50
Results (0):
Cursor.after:   skip=0, limit=50, len=228, size=50

The cursor should be usable as many time as needed and should, if all things equal on AppNexus side (accessing objects that didn't changed in the meantime), retrieve the same output.