Max road font size

I have forked openstreetmap-carto project and create my own tile style.
I try to enlarge street name for specific zoom, but it seems that max pixel value of text-size: is around 20 (I write 'around' because it's hard to see differences between 1 or 2 pixels height).
I thought maybe road width value is a "top border" which limits size, but even if I increase that value, street name stays the same.
I edit pure .mss styles files, and I didn't find anything related to this limitations.

What I tried is:
[zoom >= 19] { text-size: 23; }
Is it some global limitation of Mapnik or it may be related to other values?