diff --git a/tests/locking.builder.sh b/tests/locking.builder.sh
index bb6c2597f..69967e08b 100644
--- a/tests/locking.builder.sh
+++ b/tests/locking.builder.sh
@@ -5,6 +5,13 @@ env
 sleep 3
 
 touch $out
+echo CAT1
+cat $inputs
+echo CAT2
+echo -n $(cat $inputs)$text
+echo CAT3
+
+
 # Use `>>'; without proper locking this will cause text duplication.
 echo -n $(cat $inputs)$text >> $out