diff --git a/git_redmine.py b/git_redmine.py
index 889e88c..1831701 100644
--- a/git_redmine.py
+++ b/git_redmine.py
@@ -609,6 +609,7 @@ def clean():
     repo = get_repo()
     repo.git.fetch(prune=True)
     api = get_redmine_api()
+    api.engine.chunk = 10
     issue_re = re.compile(r'wip/([0-9]+)')
     issues_to_branch = {}