SCSS conversion error: undefined variable

[caityp]

Trying to build a site with the centrarium theme, running $ bundle exec jekyll serve and getting the following conversion error:

Conversion error: Jekyll::Converters::Scss encountered an error while converting 'css/main.scss':
Undefined variable: "$md-break-point". on line 65
jekyll 3.6.2 | Error: Undefined variable: "$md-break-point". on line 65

The problem is, I can't find the $md-break-point variable in any of my .scss files and don't know what line 65 is referring to.

I have installed:

bourbon 5.0.0
bitters 1.8.0
neat 2.1.0
jekyll 3.6.2

The main.scss file looks like this:

@charset "utf-8";

// Import partials from sass_dir (defaults to _sass)
// Includes Bourbon, Neat, and Bitters (thanks, thoughtbot!)

@import
"bourbon/bourbon",
"base/base",
"neat/neat",
"layout"
;

I'm new to sass/css with jekyll - any thoughts would help! Thanks.
repo: https://github.com/caityp/caityp.github.io

[bencentra]

That variable also doesn't exist in this project, so I'm not sure what would be causing it.

I just pushed some dependency updates to the project and I am not currently seeing that error.