diff --git a/process-repository.py b/process-repository.py
index 9c93868..dc96f2c 100644
--- a/process-repository.py
+++ b/process-repository.py
@@ -104,7 +104,7 @@ def main():
                 logger.info(
                     f">> Will tag issue #{issue["number"]} with '{issue_stale_tag}'"
                 )
-                issue_update_labels.add(issue_stale_tag)
+                issue_update_labels.append(issue_stale_tag)
 
                 gitea.update_issue_labels(
                     issue_number=issue["number"],
@@ -176,7 +176,7 @@ def main():
                 logger.info(
                     f">> Will tag pull request #{pull_request["number"]} with '{pull_request_stale_tag}'"
                 )
-                pull_request_update_labels.add(pull_request_stale_tag)
+                pull_request_update_labels.append(pull_request_stale_tag)
 
                 gitea.update_pull_requests(
                     pull_request_number=pull_request["number"],