diff --git a/fdroidserver/checkupdates.py b/fdroidserver/checkupdates.py
index b4a6e631..9ed93298 100644
--- a/fdroidserver/checkupdates.py
+++ b/fdroidserver/checkupdates.py
@@ -769,6 +769,10 @@ def push_commits(branch_name='checkupdates'):
     * https://docs.gitlab.com/ee/user/project/push_options.html
 
     """
+    if branch_name != "checkupdates":
+        if callable(getattr(git.SymbolicReference, "_check_ref_name_valid", None)):
+            git.SymbolicReference._check_ref_name_valid(branch_name)
+
     git_repo = git.Repo.init('.')
     upstream_main = get_upstream_main_branch(git_repo)
     files = set()
@@ -783,6 +787,10 @@ def push_commits(branch_name='checkupdates'):
     if not files:
         return
 
+    # https://git-scm.com/docs/git-check-ref-format Git refname can't end with .lock
+    if branch_name.endswith(".lock"):
+        branch_name = f"{branch_name}_"
+
     remote = git_repo.remotes.origin
     if branch_name in remote.refs:
         if not get_changes_versus_ref(git_repo, f'origin/{branch_name}', files[0]):