Issue while uploading app with ALTool

I am currently trying to use ALTool to upload my IPA.

This is the commands I am using (with sensitive data obfuscated):

Code Block 
xcrun altool --validate-app -f my-ipa-file.ipa -t ios --apiKey "MYAPIKEY" --apiIssuer "MYISSUERID"
xcrun altool --upload-app -f my-ipa-file.ipa -t ios --apiKey "MYAPIKEY" --apiIssuer "MYISSUERID"

My private key (p8) is located at

Code Block 
 ./private_keys/AuthKey_MYAPIKEY.p8

According to the altool --help command the tool will look in the following directories (in order) for a p8 file named AuthKey_<apikey>.p8:

• ./private_keys

• ~/private_keys

• ~/.private_keys

• ~/.appstoreconnect/private_keys

Considering the p8 file is in the first folder of that list, this should work.
And for the --validate-app call, it does actually work. The calls to App Store Connect are made, the app validates and if there are any errors from App Store Connect they return as expected.

However, for some reason the --upload-app command always returns with the same error:

Code Block 
2020-09-01 14:24:40.934 altool[28265:119010] * Error: Error uploading 'my-ipa-file.ipa'.
2020-09-01 14:24:40.934 altool[28265:119010] * Error: code -18000 (Could not locate the private key file: AuthKey_MYAPIKEY.p8)

For some reason it seems --upload-app doesn't properly load the p8 file in ./private_keys/ while --validate-app does.

Placing the p8 file in one of the other 3 folders (~/private_keys etc.) does work for both validate and upload as a temporary workaround. But I prefer to use ./private_keys.

Is this a bug or is there something I'm missing?