Help! LM2903 Hysteresis varies over temperature

LM2903 Hysteresis varies over temperature

Hi,
I am trying to create small current detect circuit using LM2903 (comparator).
Objective is to detect if current is lower than 4 uA. (Range of I1 is 0uA to 1800 uA)
R4 is there to build up the Voltage which is input(+) to comparator. R1 and R5 are voltage divider to give Vref (equivalent to 4 to 5 uA). The circuit is working fine during simulation. When I test the physical circuit at 25C ~ 85C it is working too.
But when I test it at -40C, hysteresis become zero. When input(-) approaches to threshold (input+) output started to oscillate, switching 1 and 0.:???:
why does hysteresis width change across temperature? Initially i created the circuit with two diodes where R4 and R5 are right now. When hysteresis became zero at -40C, i blamed two diodes and replaced them with resistors. Now same thing happen with new design too.
Datasheet said Input Voltage range is -0.3V to +36V. So it should work, shouldn't it?
Please help, I have no idea where went wrong.
Thanking in advance.