diff --git a/src/cmd-build b/src/cmd-build
index fa1c826810..b9832a13ee 100755
--- a/src/cmd-build
+++ b/src/cmd-build
@@ -374,11 +374,11 @@ if [ ! -f /lib/coreos-assembler/.clean ]; then
     src_location="bind mount"
 fi
 
-# And create the ostree repo tarball containing the commit
-ostree_tarfile_path=${name}-${buildid}-ostree.${basearch}.tar
+# And create the ostree repo export containing the commit
 ostree_tarfile_sha256=
 if [ "${commit}" == "${previous_commit}" ] && \
     [ -f "${previous_builddir}/${previous_ostree_tarfile_path}" ]; then
+    ostree_tarfile_path=$(jq -r '.images.ostree.path' < "${previous_builddir}/meta.json")
     cp-reflink "${previous_builddir}/${previous_ostree_tarfile_path}" "${ostree_tarfile_path}"
     ostree_tarfile_sha256=$(jq -r '.images.ostree.sha256' < "${previous_builddir}/meta.json")
     # backcompat: allow older build without this field
@@ -386,22 +386,30 @@ if [ "${commit}" == "${previous_commit}" ] && \
         ostree_tarfile_sha256=
     fi
 else
-    ostree init --repo=repo --mode=archive
-    # Pass the ref if it's set
-    # shellcheck disable=SC2086
-    if ! ostree pull-local --repo=repo "${tmprepo}" "${buildid}" ${ref}; then
-        echo '(maybe https://github.com/coreos/coreos-assembler/issues/972 ?)'
-        exit 1
-    fi
-    # Don't compress; archive repos are already compressed individually and we'd
-    # gain ~20M at best. We could probably have better gains if we compress the
-    # whole repo in bare/bare-user mode, but that's a different story...
-    tar -cf "${ostree_tarfile_path}".tmp -C repo .
+    ostree_format=$(jq -r '.["ostree-format"]' < "${image_json}")
+    case "${ostree_format}" in
+        null|tar)
+            ostree_tarfile_path=${name}-${buildid}-ostree.${basearch}.tar
+            ostree init --repo=repo --mode=archive
+            # Pass the ref if it's set
+            # shellcheck disable=SC2086
+            if ! ostree pull-local --repo=repo "${tmprepo}" "${buildid}" ${ref}; then
+                echo '(maybe https://github.com/coreos/coreos-assembler/issues/972 ?)'
+                exit 1
+            fi
+            # Don't compress; archive repos are already compressed individually and we'd
+            # gain ~20M at best. We could probably have better gains if we compress the
+            # whole repo in bare/bare-user mode, but that's a different story...
+            tar -cf "${ostree_tarfile_path}".tmp -C repo .
+            rm -rf repo
+            ;;
+        oci)
+            ostree_tarfile_path="${name}-${buildid}-ostree.${basearch}.ociarchive"
+            rpm-ostree ex-container 'export' --repo="${tmprepo}" "${buildid}" oci-archive:"${ostree_tarfile_path}".tmp
+            ;;
+        *) fatal "Unknown ostree-format: ${ostree_format}"
+    esac
     /usr/lib/coreos-assembler/finalize-artifact "${ostree_tarfile_path}"{.tmp,}
-    rm -rf repo
-fi
-
-if [ -z "${ostree_tarfile_sha256:-}" ]; then
     ostree_tarfile_sha256=$(sha256sum "${ostree_tarfile_path}" | awk '{print$1}')
 fi
 
diff --git a/src/cosalib/cmdlib.py b/src/cosalib/cmdlib.py
index 0df5143db7..7d976ceaa3 100644
--- a/src/cosalib/cmdlib.py
+++ b/src/cosalib/cmdlib.py
@@ -249,10 +249,29 @@ def import_ostree_commit(repo, buildpath, buildmeta, force=False):
         return
 
     # extract in a new tmpdir inside the repo itself so we can still hardlink
-    with tempfile.TemporaryDirectory(dir=repo) as d:
-        subprocess.check_call(['tar', '-C', d, '-xf', tarfile])
-        subprocess.check_call(['ostree', 'pull-local', '--repo', repo,
-                               d, commit])
+    if tarfile.endswith('.tar'):
+        with tempfile.TemporaryDirectory(dir=repo) as d:
+            subprocess.check_call(['tar', '-C', d, '-xf', tarfile])
+            subprocess.check_call(['ostree', 'pull-local', '--repo', repo,
+                                   d, commit])
+    elif tarfile.endswith('.ociarchive'):
+        # We do this in two stages, because right now ex-container only writes to
+        # non-archive repos.  Also, in the privileged case we need sudo to write
+        # to `repo-build`, though it might be good to change this by default.
+        if os.environ.get('COSA_PRIVILEGED', '') == '1':
+            build_repo = os.path.join(repo, '../../cache/repo-build')
+            subprocess.check_call(['sudo', 'rpm-ostree', 'ex-container', 'import', '--repo', build_repo,
+                                   '--write-ref', buildmeta['buildid'], 'oci-archive:' + tarfile])
+            subprocess.check_call(['sudo', 'ostree', f'--repo={repo}', 'pull-local', build_repo, buildmeta['buildid']])
+            uid = os.getuid()
+            gid = os.getgid()
+            subprocess.check_call(['sudo', 'chown', '-hR', f"{uid}:{gid}", repo])
+        else:
+            with tempfile.TemporaryDirectory() as tmpd:
+                subprocess.check_call(['ostree', 'init', '--repo', tmpd, '--mode=bare-user'])
+                subprocess.check_call(['rpm-ostree', 'ex-container', 'import', '--repo', tmpd,
+                                       '--write-ref', buildmeta['buildid'], 'oci-archive:' + tarfile])
+                subprocess.check_call(['ostree', f'--repo={repo}', 'pull-local', tmpd, buildmeta['buildid']])
 
 
 def get_basearch():
diff --git a/tests/test_cosalib_cmdlib.py b/tests/test_cosalib_cmdlib.py
index 299d01009b..0efa1c8d14 100644
--- a/tests/test_cosalib_cmdlib.py
+++ b/tests/test_cosalib_cmdlib.py
@@ -122,7 +122,7 @@ def __call__(self, *args, **kwargs):
                     'ostree', 'init', '--repo', tmpdir, '--mode=archive']
             if self.check_call_count == 1:
                 assert args[0][0:2] == ['tar', '-C']
-                assert args[0][3:5] == ['-xf', './tarfile']
+                assert args[0][3:5] == ['-xf', './tarfile.tar']
             if self.check_call_count == 2:
                 assert args[0][0:4] == [
                     'ostree', 'pull-local', '--repo', tmpdir]
@@ -142,7 +142,7 @@ def monkeyspcall(*args, **kwargs):
         'ostree-commit': 'commit',
         'images': {
             'ostree': {
-                'path': 'tarfile'
+                'path': 'tarfile.tar'
             }
         }
     }