"could not determine a source map reference"

I noticed this in the output to a sentry-cli command:

~/index.android.bundle (sourcemap at index.android.bundle.map) - warning: could not determine a source map reference (Could not auto-detect referenced sourcemap for ~/index.android.bundle.)

Why would this happen? Here’s how I’m calling sentry-cli:

sentry-cli releases files $RELEASE_ID upload-sourcemaps --dist $VERSION_CODE --bundle $BUNDLE --bundle-sourcemap $SOURCEMAP

where these variables are substituted for the appropriate values. index.android.bundle and index.android.bundle.map both exist, but are in different directories. Could that be the cause of this?

I tried generating both files in the same directory but still see that warning, so that doesn’t seem relevant.