`font-weight` in css is not working

I was trying to set `font-weight: bold;` or `font-weight: 700;` (or any other weight values) but in the converted PDF, the font weight is not applied (I was using macOS). I wasn't using any fancy font family:

```
h1 {
font-family: Arial, Helvetica, sans-serif;
font-weight: bold;
}
```

Other css rules worked just fine though.

Does anyone happen to have the same problem? Am I missing anything? Thanks!