Bug: The "port" option you specified conflicts with the port of your application

[cbetta]

When running netlify dev for my Gatsby app I suddenly get this error:

Error: The "port" option you specified conflicts with the port of your application. Please use a different value for "port"

I have no idea how to resolve this, I've tried changing varying the target port and functions port, but to no change.

- Version affected

This only seems to affect version 2.47 and higher

- Local Environment Information

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Environment Info │
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System:
OS: macOS 10.15.4
CPU: (12) x64 Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz
Binaries:
Node: 13.8.0 - ~/.nvm/versions/node/v13.8.0/bin/node
Yarn: 1.22.4 - ~/code/box/developer.box.com-framework/node_modules/.bin/yarn
npm: 6.14.3 - ~/.nvm/versions/node/v13.8.0/bin/npm
Browsers:
Chrome: 84.0.4128.3
Firefox: 75.0
Safari: 13.1

[cbetta]

Found the issue, I had the following in my netlify.toml

[dev]
  port = 8000

Removing this resolved the issue.