2020.3: repeating-linear-gradient support

Having upgraded to 2020.3, I am still seeing a false error on a perfectly valid repeating-linear-gradient CSS declaration.

Code:

.not-available {
    background: repeating-linear-gradient(-45deg, transparent 0 5px, rgba(170, 68, 68, 0.2) 5px 10px);
    cursor: not-allowed;
}

R# error: "Expected ,."

The declaration is perfectly valid according to MDN:

repeating-linear-gradient(  [ <angle> | to <side-or-corner> ,]? <color-stop-list> )
                            \---------------------------------/ \---------------/
                              Definition of the gradient line   List of color stops

where <side-or-corner> = [left | right] || [top | bottom]
  and <color-stop-list> = [ <linear-color-stop> [, <color-hint>? ]? ]#, <linear-color-stop>
  and <linear-color-stop> = <color> [ <color-stop-length> ]?
  and <color-stop-length> = [ <percentage> | <length> ]{1,2}
  and <color-hint> = [ <percentage> | <length> ]

<linear-color-stop>
A color-stop's <color> value, followed by one or two optional stop positions, ...

The gradient works in all supported browsers: Demo

ReSharper 2020.3 Build 203.0.20201211.113035 built on 2020-12-11
Visual Studio Professional 2019 (Version 16.8.30804.86).