diff --git a/doc/todo/pass_-S_to_commit-tree.mdwn b/doc/todo/pass_-S_to_commit-tree.mdwn
new file mode 100644
index 0000000000..ee6ff2d589
--- /dev/null
+++ b/doc/todo/pass_-S_to_commit-tree.mdwn
@@ -0,0 +1,10 @@
+In git 2.9.0, commit-tree does not respect commit.gpgsign on its own,
+which it used to.
+
+So, in Git.Branch.commitTree, it needs to check if gpgsign is set,
+and pass -S to commit-tree.
+
+(commit-tree -S works in older versions of git, so this can
+be done without version checks.)
+
+--[[Joey]]