Build Error with v1.17.0

[rydurham]

I tried updating to v1.17.0 (from v1.16.0) just now and I ran into a build error. Has anyone else encountered this?

I used these steps to upgrade:

$ git pull
$ git checkout v1.17.0
$ npm install
$ npm run build

The build task does not complete. Instead I am getting this error:

info  - Loaded env from /home/forge/DOMAIN/.env
info  - Using webpack 4. Reason: custom webpack configuration in next.config.js https://nextjs.org/docs/messages/webpack5
info  - Checking validity of types
(node:2864480) UnhandledPromiseRejectionWarning: Error: [object Object] is not a PostCSS plugin
    at Processor.normalize (/home/forge/DOMAIN/node_modules/postcss/lib/processor.js:168:15)
    at new Processor (/home/forge/DOMAIN/node_modules/postcss/lib/processor.js:52:25)
    at postcss (/home/forge/DOMAIN/node_modules/postcss/lib/postcss.js:55:10)
    at module.exports (/home/forge/DOMAIN/node_modules/cssnano-simple/src/index.js:54:10)
    at minifyCss (/home/forge/DOMAIN/node_modules/next/dist/build/webpack/plugins/font-stylesheet-gathering-plugin.js:1:554)
    at /home/forge/DOMAIN/node_modules/next/dist/build/webpack/plugins/font-stylesheet-gathering-plugin.js:25:432
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
(node:2864480) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 455)
(node:2864480) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
info  - Creating an optimized production build
Failed to compile.

Error: [object Object] is not a PostCSS plugin


> Build error occurred
Error: > Build failed because of webpack errors
    at /home/forge/DOMAIN/node_modules/next/dist/build/index.js:17:924
    at async Span.traceAsyncFn (/home/forge/DOMAIN/node_modules/next/dist/telemetry/trace/trace.js:6:584)

Does anyone have any thoughts or advice?

Interestingly I tried running those same steps for v1.16.0 again and I am getting the same error.

[rydurham]

I turns out that I ran npm install without first removing the existing package-lock.json file which ultimately led to a dependency mismatch. Removing the package-lock.json file before running the installation step resolved the problem.