diff --git a/c/todo.txt b/c/todo.txt
index 5d8657451..6ed3da5a2 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -11,6 +11,8 @@ BUGFIXES
   x=9223372036854775802,y=-9223372036854775806
   x=9223372036854775805,y=-9223372036854775802
 
+$ mlr --from s put 'tee > "boo.".$a, mapexcept($*,"a")'
+
 ================================================================
 5.3.0 TO DO: