Selector with attribute matching throws exception on WebGL build

[Llermy]

When it happens:
At Stylesheet stylesheet = parser.Parse(css);, whenever the CSS string contains a selector with attribute matching and only in the WebGL build, in the editor it works fine. It happens only when CSS string contains attribute matching as in a[href="https://example.org"] and not when asking a selector to simply contain an attribute as in a[title].

Exception that is thrown:

MissingMethodException: Constructor on type 'ExCSS.AttrMatchSelector' not found.
  at System.RuntimeType.CreateInstanceImpl (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, System.Object[] args, System.Globalization.CultureInfo culture, System.Object[] activationAttributes, System.Threading.StackCrawlMark& stackMark) [0x00000] in <00000000000000000000000000000000>:0 
 
(Filename: currently not available on il2cpp Line: -1)

[Llermy]

Btw, I'm using ExCSS installed with the latest version of NuGet inside Unity 2019.4.40f1.