Using CSS property content to read value from an attribute using glamor

Question

Using glamor (css framework) and react, I want to style something to show the content of an attribute like this:

<div data-tooltip="show this string" {...css(styles.toolTip) }>
...some text
</div>

Then for the toolTip style i have something like this:

...
'&:after'. {
  content: 'attr(data-tooltip)',
  ...
}
...

Because of glamor i get the text "attr(data-tooltip)" in my content, which is not what i want - i want the content of the data-tooltip attribute, which works fine in pure css, but somehow does not work with glamor.

I'm using version 2.20.30 of glamor.