F5 incorrectly discovered as 32-Bit

Our F5 Loadbalancers (BIG-IP 11.6.0) are being discovered with 32-Bit ports, although they export all data as 64-Bit.
Rediscovering the devices did not help (SNMP v2c).
F5 documentation states that all counters are 64-Bit:
https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/tmos_management_guide_10_1/tmos_snmp.html

Running Observium 0.15.10.7069 (4th October 2015).