Trouble when using RBGA in Radial Gradient

[thehung2224]

I'm having a bit of trouble with RGBA when using with Radial Gradient. I'm using LESSHat 3.

.background-image(
    radial-gradient(circle farthest-corner at center center, 
        rgba(85,85,85, 0.3) 0%, 
        rgba(81,81,81,0.3) 50%, 
        rgba(0,0,0,0.5) 100%)
);

When checking CSS with Firebug, it like this

background-image: 
    radial-gradient(circle farthest-corner at center center , 
        rgba(85, 85, 85, 0) 0%, 
        rgba(81, 81, 81, 0) 50%, 
        #000000 100%
    );

But when using with interpolation, everything works fine.

.background-image(~"
    radial-gradient(circle farthest-corner at center center, 
        rgba(85,85,85, 0.3) 0%, 
        rgba(81,81,81,0.3) 50%, 
        rgba(0,0,0,0.5) 100%)"
);

Hope everyone can give me advice for this issue. Thank in advance.