Pixel values in custom property names are converting too

[ryanve]

In our codebase we have some custom properties like --rem-16px: 1rem

If I run postcss-pxtorem with these then these variables are renamed like --rem-1rem: 1rem but I didn't expect that the property name would be replaced. Not sure if it's a big issue because I plan to remove those and replace with this plugin but still maybe there is a way to prevent that or is that the desired behavior?

2:14	⚠  variable '--rem-1rem' is undefined and used without a fallback [postcss-custom-properties]
45:14	⚠  variable '--rem-1rem' is undefined and used without a fallback [postcss-custom-properties]
48:14	⚠  variable '--rem-2rem' is undefined and used without a fallback [postcss-custom-properties]