error when evicting if data is already evicted

Flushing database.
Setting 'a' to '1'.
Stopping NorthScale server [ OK ]
Starting NorthScale server [ OK ]
Sleeping 5 seconds.
Evicting 'a' to disk.
Traceback (most recent call last):
File "/opt/NorthScale/bin/ep_engine/management/flushctl.py", line 33, in ?
c.execute()
File "/opt/NorthScale/1.6.0beta2rc1/bin/ep_engine/management/clitool.py", line 35, in execute
getattr(mc, f[0])(*sys.argv[3:])
File "/opt/NorthScale/bin/ep_engine/management/mc_bin_client.py", line 200, in evict_key
return self._doCmd(memcacheConstants.CMD_EVICT_KEY, key, '')
File "/opt/NorthScale/bin/ep_engine/management/mc_bin_client.py", line 87, in _doCmd
return self._handleSingleResponse(opaque)
File "/opt/NorthScale/bin/ep_engine/management/mc_bin_client.py", line 80, in _handleSingleResponse
cmd, opaque, cas, keylen, extralen, data = self._handleKeyedResponse(myopaque)
File "/opt/NorthScale/bin/ep_engine/management/mc_bin_client.py", line 76, in _handleKeyedResponse
raise MemcachedError(errcode, rv)
mc_bin_client.MemcachedError: Memcached error #7
ep_bg_fetched: 0
Getting the value for 'a'.
a = 1
ep_bg_fetched: 1

If I do a get before I do the evict, the evict doesn't get an error and ep_bg_fetched gets incremented. Is this expected behavior?

All of this is done using mc_bin_client/scripts in ep_engine/management over 11210.