whisper-resize.py fails with error message

We're running carbon-0.9.8 and I started with the default storage schema and changed it to:

[everything_1min_13months]
priority = 100
pattern = .*
retentions = 60:565920

I restarted carbon-cache and then ran whisper-resize on one of the databases but got this error:

<email address hidden>[/opt/graphite/storage/whisper/nfs/vg8_bo3/server_2] whisper-resize.py 60:565920 average_write_kb_sec.wsp
Traceback (most recent call last):
  File "/usr/bin/whisper-resize.py", line 70, in ?
    new_archives = [ parseRetentionDef(retentionDef) for retentionDef in args[1:] ]
  File "/usr/bin/whisper-resize.py", line 19, in parseRetentionDef
    (precision, points) = retentionDef.strip().split(':')
ValueError: need more than 1 value to unpack