diff --git a/src/hb-cairo.cc b/src/hb-cairo.cc
index 7b4d529b3..3a2d36d59 100644
--- a/src/hb-cairo.cc
+++ b/src/hb-cairo.cc
@@ -36,6 +36,9 @@
 #include "hb-utf.hh"
 
 
+/* TODO Error handling in cairo set_user_data calls? */
+
+
 /**
  * SECTION:hb-cairo
  * @title: hb-cairo