diff --git a/include/rebar.hrl b/include/rebar.hrl
index bc46b1d..b338fc2 100644
--- a/include/rebar.hrl
+++ b/include/rebar.hrl
@@ -1,3 +1,6 @@
+%% TODO: rename FAIL to ABORT once we require at least R13B04 for
+%% building rebar. Macros with different arity were not supported by the
+%% compiler before 13B04.
 -define(FAIL, rebar_utils:abort()).
 -define(ABORT(Str, Args), rebar_utils:abort(Str, Args)).