### OS? > Mac OS Sierra 10.12.1 ### Versions. > angular-cli: 1.0.0-beta.20-4 node: 6.9.1 os: darwin x64 ### Repro steps. > Using SCSS: Have a component's scss file with a prefix-able property (for instance: display: flex); - Running `ng serve`, the output will have various prefixed CSS properties for display: flex; - Running `ng serve --prod`, the output will only have the actual written display: flex, **without any prefixes**.