Source maps don't generate

[Nowaker]

• I tried updating to the latest version
• I Am on Linux
  • Other: Arch Linux
• I am on macOS 10.14
• I'm on Docker
  • I understand Docker may be unsupported

Description

Steps

Neither of these configs generate source maps for either SCSS:

assets:
  source_maps: true
  compression: false
  prefix: '/assets'
  sources:
  - assets
  - assets/js

assets:
  source_maps: true
  compression: true
  prefix: '/assets'
  sources:
  - assets
  - assets/js

Adding JEKYLL_ENV=production or JEKYLL_ENV=development on top of the config above still doesn't trigger the generation of source maps.

Output

[2019-08-22 18:21:37] ERROR `/assets/css/site-f35f10fd08b6aa61d32980178990453f2e8f8f1dc43e5fe411ad14a31bf44821.css.map' not found.
[2019-08-22 18:20:41] ERROR `/assets/js/site-b534dbc9c94ee86fec4925290f78053cfc0affe8f0d2c461bace7428df0c4983.js.map' not found.

URLs without a .map work correctly and display a compressed JS/CSS.

Expected

Source maps should be generated.