"Unable to resolve POM" for jars in flatDir repo

[TheoLassonder]

We have some jars that can't be referenced from Maven but are instead in a flatDir repo:

plugins {
    id 'org.cyclonedx.bom' version '1.7.4'
}

cyclonedxBom {
    outputFormat = "json"
}

repositories {
    google()
    mavenCentral()
    flatDir { dirs "$rootProject.projectDir/libs" }
}

dependencies {
    implementation 'oracle:ojdbc11:19c' // Resolves to flatDir repo
}

But this errors when running the cyclonedx task:

$ ./gradlew cyclonedx

> Task :cyclonedxBom
An unexpected issue occurred attempting to create a PackageURL for :myproject:unspecified
Unable to resolve POM for oracle:ojdbc11:19c: org.gradle.api.internal.artifacts.ivyservice.DefaultLenientConfiguration$ArtifactResolveException: Could not resolve all files for configuration ':detachedConfiguration179'.

I'd expect an SBOM to still be created. For example cdxgen does create an SBOM for this project with no error.

Is there any way to make this work?