Why do I receive a warning for transfer function having complex valued coefficients?

I've defined a complex filter transfer function with, of course, complex valued coefficients; The transfer function of the complex filter was designed such that its negative freqs response and positive freqs response isn't symmetrical about freq = 0 (DC), but Matlab complains about it. Why?

Warning: The numerator or denominator of this transfer function has complex-valued coefficients. 
> In ctrlMsgUtils.warning (line 25)
  In tf (line 351)
  In rxcktconfig (line 156)

The script "rxcktconfig.m" contains my codes it complains about.