diff --git a/TODO b/TODO
index 5030e217..210b83e8 100644
--- a/TODO
+++ b/TODO
@@ -10,3 +10,4 @@
 * Fix rubinius to allow setting @vcall_style variable in Rubinius::AST::Send nodes.
 * Aggregate warnings on missing spec files
 * Make sure loader does not change visibility of injected mutants
+* Collect emmited mutants per subtree and do not emit the same subtree twice.