diff --git a/src/cmd-build b/src/cmd-build
index 868b7d20d9..aed0311e97 100755
--- a/src/cmd-build
+++ b/src/cmd-build
@@ -156,7 +156,6 @@ fi
 image_config_checksum=$(< "${image_input}" sha256sum_str)
 if [ -n "${previous_build}" ]; then
     previous_image_input_checksum=$(jq -r '.["coreos-assembler.image-input-checksum"]' < "${previous_builddir}/meta.json")
-    previous_image_genver=$(jq -r '.["coreos-assembler.image-genver"]' < "${previous_builddir}/meta.json")
 fi
 echo "Image Config checksum: ${image_config_checksum}"
 
@@ -277,14 +276,8 @@ fi
 
 image_input_checksum=$( (echo "${commit}" && echo "${image_config_checksum}") | sha256sum_str)
 echo "New image input checksum: ${image_input_checksum}"
-version=$(ostree --repo="${tmprepo}" show --print-metadata-key=version "${commit}" | sed -e "s,',,g")
-if [ "${previous_commit}" = "${commit}" ] && [ -n "${previous_image_genver:-}" ]; then
-    image_genver=$((previous_image_genver + 1))
-    buildid="${version}"-"${image_genver}"
-else
-    image_genver=0
-    buildid="${version}"
-fi
+init_build_meta_json "${commit}" tmp/
+buildid=$(jq -r '.["buildid"]' < tmp/meta.json)
 echo "New build ID: ${buildid}"
 
 "${dn}"/write-commit-object "${tmprepo}" "${commit}" "$(pwd)"
@@ -333,14 +326,12 @@ fi
 # summary could have double quotes: https://github.com/coreos/coreos-assembler/issues/327
 #
 # shellcheck disable=SC2046 disable=SC2086
-cat > tmp/meta.json <<EOF
+cat > tmp/buildmeta.json <<EOF
 {
- "buildid": "${buildid}",
  "name": "${name}",
  "summary": "${summary//\"/\\\"}",
  "coreos-assembler.build-timestamp": "${build_timestamp}",
  "coreos-assembler.image-config-checksum": "${image_config_checksum}",
- "coreos-assembler.image-genver": "${image_genver}",
  "coreos-assembler.image-input-checksum": "${image_input_checksum}",
  "coreos-assembler.code-source": "${src_location}",
  "coreos-assembler.container-config-git": $(jq -M '.git' ${PWD}/coreos-assembler-config-git.json)
@@ -378,7 +369,7 @@ fi
 
 # Merge all the JSON; note that we want ${composejson} first
 # since we may be overriding data from a previous build.
-cat "${composejson}" "${overridesjson}" tmp/meta.json tmp/diff.json tmp/images.json tmp/cosa-image.json "${commitmeta_input_json}" | jq -s add > meta.json
+cat "${composejson}" "${overridesjson}" tmp/meta.json tmp/buildmeta.json tmp/diff.json tmp/images.json tmp/cosa-image.json "${commitmeta_input_json}" | jq -s add > meta.json
 
 # Filter out `ref` if it's temporary
 if [ -n "${ref_is_temp}" ]; then
diff --git a/src/cmdlib.sh b/src/cmdlib.sh
index f571c176b2..29c263957b 100755
--- a/src/cmdlib.sh
+++ b/src/cmdlib.sh
@@ -679,6 +679,16 @@ from cosalib.builds import Builds
 print(Builds('${workdir:-$(pwd)}').get_build_dir('${buildid}'))")
 }
 
+init_build_meta_json() {
+    local ostree_commit=$1; shift
+    local dir=$1; shift
+    (python3 -c "
+import sys
+sys.path.insert(0, '${DIR}')
+from cosalib.builds import Builds
+print(Builds('${workdir:-$(pwd)}').init_build_meta_json('${ostree_commit}', '${dir}'))")
+}
+
 get_latest_qemu() {
     local latest builddir
     latest=$(get_latest_build)
diff --git a/src/cosalib/builds.py b/src/cosalib/builds.py
index 66dbd1bb2a..ca98b296ff 100644
--- a/src/cosalib/builds.py
+++ b/src/cosalib/builds.py
@@ -2,8 +2,13 @@
 Builds interacts with builds.json
 """
 
+import json
 import os
 import semver
+import gi
+
+gi.require_version('OSTree', '1.0')
+from gi.repository import Gio, OSTree
 
 from cosalib.cmdlib import (
     get_basearch,
@@ -84,6 +89,38 @@ def insert_build(self, build_id, basearch=None):
                 ]
             })
 
+    def init_build_meta_json(self, ostree_commit, destdir):
+        """
+        Given a new ostree version, initialize a new coreos-assembler
+        build by writing a `meta.json` in destdir.
+        """
+        repopath = os.path.join(self._workdir, 'tmp/repo')
+        r = OSTree.Repo.new(Gio.File.new_for_path(repopath))
+        r.open(None)
+        [_, rev] = r.resolve_rev(ostree_commit, True)
+        [_, commit, _] = r.load_commit(rev)
+        commitmeta = commit.get_child_value(0)
+        version = commitmeta.unpack()['version']
+        image_genver = 0
+        buildid = version
+        genver_key = 'coreos-assembler.image-genver'
+        if not self.is_empty():
+            previous_buildid = self.get_latest()
+            metapath = self.get_build_dir(previous_buildid) + '/meta.json'
+            with open(metapath) as f:
+                previous_buildmeta = json.load(f)
+            previous_commit = previous_buildmeta['ostree-commit']
+            previous_image_genver = int(previous_buildmeta[genver_key])
+            if previous_commit == ostree_commit:
+                image_genver = previous_image_genver + 1
+                buildid = f"{version}-{image_genver}"
+        meta = {
+            'buildid': buildid,
+            genver_key: image_genver
+        }
+        with open(destdir + '/meta.json', 'w') as f:
+            json.dump(meta, f)
+
     def bump_timestamp(self):
         self._data['timestamp'] = rfc3339_time()
         self.flush()