The name of the parts can't have upper case letters. I tried defining a part called libArcus and got the following error: Issues while validating snapcraft.yaml: The 'parts' property does not match the required schema: Additional properties are not allowed ('libArcus' was unexpected) The docs don't mention anything about the parts being all lower-case. If this was on purpose, it must be documented and a better error should be reported to the user.