Error when building fedora rawhide

I am trying to build Fedora Silverblue but am receiving an error:

error: importing RPMs: /proc/self/fd/9/cache/repomd/fedora-rawhide-rpmostree-unset-releasever-x86_64/packages/kernel-core-5.11.0-0.rc4.129.fc34.x86_64.rpm could not be verified

Here are the steps I am taking:

cd /srv
git clone https://pagure.io/workstation-ostree-config.git

# Set up build environment
mkdir /srv/repo /srv/cache 2>/dev/null
ostree init --repo=/srv/repo --mode=archive

# Compose tree
rpm-ostree compose tree \
	--unified-core \
	--repo=/srv/repo \
	--cachedir=/srv/cache \
	/srv/workstation-ostree-config/fedora-silverblue.yaml