Snapshot error with option SKIP_FLUSH

Hi,
I have the following excpetion when I try to do a snapshot on HBase (0.98.0.2.1) :
snapshot ‘myTable1′, ‘mySnapshot_myTable1′, {SKIP_FLUSH => true}
NameError: uninitialized constant SKIP_FLUSH

When I don’t use the option {SKIP_FLUSH => true}, it works.
Any idea ??
thanks in advance for your help.
regards,