diff --git a/scripts/get-latest-version.sh b/scripts/get-latest-version.sh
index 840bf5e..4e3c2b8 100755
--- a/scripts/get-latest-version.sh
+++ b/scripts/get-latest-version.sh
@@ -24,8 +24,9 @@ if [ -n "$tag" ]; then
   echo "version=${tag#v}"
   echo "ref=$tag"
 else
-  sha=$(git ls-remote "$UPSTREAM_URL" refs/heads/main | cut -c1-12)
+  # ref must stay the full sha: `git fetch <sha>` rejects abbreviated ids.
+  sha=$(git ls-remote "$UPSTREAM_URL" refs/heads/main | awk '{print $1}')
   [ -n "$sha" ] || { echo "ERROR: cannot resolve upstream main" >&2; exit 1; }
-  echo "version=0.0.0-git.$sha"
+  echo "version=0.0.0-git.${sha:0:12}"
   echo "ref=$sha"
 fi