Collectd-mod-sensors - only temp sensors in LuCI

I've enabled all sensors in collectd-mod-sensors and they are collected properly in /tmp/rrd but are not generated in /tmp/rrdimg and thus not presented in LuCI/WebUI. The voltages and fan rpms are missing.

Any idea what's wrong here?

r10099 x86-64

$ sensors 
coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +34.0°C  (high = +80.0°C, crit = +99.0°C)
Core 0:        +33.0°C  (high = +80.0°C, crit = +99.0°C)
Core 1:        +33.0°C  (high = +80.0°C, crit = +99.0°C)
Core 2:        +31.0°C  (high = +80.0°C, crit = +99.0°C)
Core 3:        +33.0°C  (high = +80.0°C, crit = +99.0°C)

f71808a-isa-0290
Adapter: ISA adapter
in0:          +1.62 V  
in1:          +0.78 V  
in2:          +2.04 V  
in3:          +2.04 V  
in7:          +1.60 V  
in8:          +1.74 V  
fan1:         846 RPM
fan2:           0 RPM  ALARM
fan3:           0 RPM  ALARM
temp1:        +29.0°C  (high = +85.0°C, hyst = +81.0°C)
                       (crit = +100.0°C, hyst = +96.0°C)  sensor = transistor
temp2:        +36.0°C  (high = +85.0°C, hyst = +81.0°C)
                       (crit = +100.0°C, hyst = +96.0°C)  sensor = transistor

Looks like its a known bug: