diff --git a/src/binary_formats.ml b/src/binary_formats.ml
index ecdc6c32..8b1a7f7d 100644
--- a/src/binary_formats.ml
+++ b/src/binary_formats.ml
@@ -2,8 +2,9 @@
 
    - numeric values are in network byte order (big endian) *)
 (* TODO: ?
-   some struct have a 'P' suffix, but are not defined in doc
-   we assume they are = to the un-suffixed ones *)
+   - some struct have a 'P' suffix, but are not defined in doc
+     we assume they are = to the un-suffixed ones
+   - some purpose (`TALER_SIGNATURE_XXX`) are missing or outdated(?) *)
 
 open Include