diff --git a/frontend/security-center.js b/frontend/security-center.js
index ff1ada0..8908301 100644
--- a/frontend/security-center.js
+++ b/frontend/security-center.js
@@ -231,6 +231,7 @@
         passkey_counter_anomaly: 'Passkey counter anomaly',
         device_revoked: 'Device access revoked', all_sessions_revoked: 'All device access revoked',
         issue_closed: 'Issue closed', pull_merged: 'Pull request merged',
+        source_branch_deleted: 'Source branch deleted',
         comment_deleted: 'Comment deleted',
         pull_review_approved: 'Pull request approved',
         pull_review_changes_requested: 'Changes requested', gitea_time_logged: 'Gitea time logged',
diff --git a/tests/test_security_center.py b/tests/test_security_center.py
index 02e225b..26e1ff9 100644
--- a/tests/test_security_center.py
+++ b/tests/test_security_center.py
@@ -6,6 +6,12 @@ from pathlib import Path
 SECURITY_CENTER = Path(__file__).parents[1] / "frontend" / "security-center.js"
 
 
+def test_source_branch_cleanup_has_a_specific_security_activity_label():
+    source = SECURITY_CENTER.read_text()
+
+    assert "source_branch_deleted: 'Source branch deleted'" in source
+
+
 def test_open_security_center_loads_all_sections_concurrently_and_is_awaitable():
     harness = f"""
 const attachSecurityCenter=require({json.dumps(str(SECURITY_CENTER))});