I guess the following should not happen (5.11.0, on both Windows/GCL and Linux/CMUCL): ,---- | (%i1) tlimit(s/(1+s^2)/sinh(s*T), s, inf); | Is T positive, negative, or zero? | | p; | Invalid call to var-expand | -- an error. To debug this try debugmode(true); `---- Best regards, Albert.