"Unknwown internal option" warning

[Urs Liska]

When I add a custom option on the command line with -dcustom-option and 
test for it in the input file using

#(if (defined? 'custom-option))


My file compiles well and respects the option, but I get a warning about 
"No such internal option: custom-option" (maybe it's differently worded, 
I'm translating).

Is there a way to suppress this warning? As said in the other thread 
this will be some 'library' kind of code so I would prefer not to 
generate warnings.

TIA
Urs