text-shadow property rgba

I am using RBGA color with text-shadow property, and the CSS Level 3
validator gives me an error: 

Missing values or unrecognized arguments.

 
#breadcrumbs {
               text-shadow: 0 1px 0 rgba(255,255,255,1);
}
 

 

Is there an error in my definition or this is a validator-error?

 

Tania Ivanova 
TransModalBots S.L.
Tlf. 942 760 280 
tania@transmodalbots.com <mailto:tania@transmodalbots.com>