System sync error

I’m attempting to request a system sync for all systems. The query part of the URL is:



?cmd=requestsystemsync&session=7788489037051019350&h=D-AUN-00533851&systemid=all&synctype=system



In the response I get:



<sync>Missing valid systemid= parameter.</sync>



If I change ‘all’ to a numeric systemId then it works. Also, I have a separate C2 account that I use for testing, and on that the ‘all’ parameter works, so I have confidence that my code is correct.



Any ideas why the ‘all’ param wouldn’t work for just one of my accounts?