radial-gradient validation

Hi all;
I'm fairly certain this is a bug in the validator but wanted to confirm:
I'm getting "Value Error : background 
<http://jigsaw.w3.org/css-validator/nullcolors.html#propdef-background> 
ellipse at center is not a radial-gradient value )"
for 
<http://jigsaw.w3.org/css-validator/validator?uri=http%3A%2F%2Fwww.briarmoon.ca%2Fhosted%2FShirleyHillBoogies%2Fhistory.html%3Fhidesidebar>my 
webpage (under development)
however reading http://dev.w3.org/csswg/css-images-3/#radial-gradients
sure seems to me to be saying that it is.
Anyone able to confirm/correct my understanding?
thanks;
Nick
BriarMoon Design
<http://jigsaw.w3.org/css-validator/validator?uri=http%3A%2F%2Fwww.briarmoon.ca%2Fhosted%2FShirleyHillBoogies%2Fhistory.html%3Fhidesidebar>