diff --git a/TODO b/TODO
index 634de11e..003eb683 100644
--- a/TODO
+++ b/TODO
@@ -26,6 +26,7 @@ Version 1.4.0:
 * Separate Pdo and Pdo entry classes.
 * Attach Pdo names.
 * Replace ec_sdo_data_t with ec_sdo_request_t.
+* Make all define underscores the same.
 
 Future issues: