Simulink/Matlab throws a warning about log of a negative number durig simulation. The signal inspector shows the number is always positive.

Simulink/Matlab throws the following warning while I try to linearize my model around an opperating point:

Warning: Log of a negative number in 'Model/Subsystem/Oxygenator/pHvirtual/Log'. Consider setting the 'Output

signal type' to complex.

The signal inspector shows the following values for the highlighted block:

The warning is thrown after I call the linearize function.

sys=linearize('Model',op1(2),io)

Running the model with simulink does not cause the warning.