FAILEDDISK not working

The FAILEDDISK command does not work on my FAS2220, ONTAP 8.1.3. Via telnet, the disk show command says I have one failed disk, yet this check insists there are no failed disks. Manual snmpwalk on the OIDs (1.3.6.1.4.1.789.1.6.4 and below) confirms the system thinks there are no failed disks when queried via SNMP. Possibly a bug in ONTAP?