Shadcn theming with opacity does not work

I have a button variant that is not changing the background opacity on hover.

        default: 'bg-primary text-primary-foreground hover:bg-primary/90',

This is the button variant I'm applying. However, it changes color on hover without any problem. For example if i apply

hover:bg-red-500

,it will work without any problem.

It's only when it comes to opacity of the background.

      primary: {
      DEFAULT: 'var(--primary)',
      foreground: 'var(--primary-foreground)',
    },

This is in my tailwind.config.mjs.

  --primary: oklch(0.8148 0.0819 225.7537);
  --primary-foreground: oklch(0.3348 0.0526 161.6917);

is the how the colors are defined. So, I'm using oklch.