diff --git a/_test_data/sandbox/clean/base.txt b/_test_data/sandbox/clean/base.txt
index 3b5599a..0adffc1 100644
--- a/_test_data/sandbox/clean/base.txt
+++ b/_test_data/sandbox/clean/base.txt
@@ -1,2 +1,3 @@
 clean stack: base branch
 purpose: baseline parent PR
+marker: 1639076