diff --git a/ChangeLog b/ChangeLog
index b1eae51ff5..5567615231 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Jan 13 11:44:32 +0100 2009 Jim Meyering <meyering@redhat.com>
+
+	* HACKING: Clarify "bool" vs. XDR/wire-format.
+
 Mon Jan 12 22:07:57 CET 2009 Daniel Veillard <veillard@redhat.com>
 
 	* docs/index.html docs/index.html.in docs/relatedlinks.html
diff --git a/HACKING b/HACKING
index ba036043ea..ca39d61d85 100644
--- a/HACKING
+++ b/HACKING
@@ -115,7 +115,10 @@ standard type like int32_t, uint32_t, uint64_t, etc.
 
 While using "bool" is good for readability, it comes with minor caveats:
  - Don't use "bool" in places where the type size must be constant across
-   all systems, like public interfaces and on-the-wire protocols.
+   all systems, like public interfaces and on-the-wire protocols.  Note
+   that it would be possible (albeit wasteful) to use "bool" in libvirt's
+   logical wire protocol, since XDR maps that to its lower-level bool_t
+   type, which *is* fixed-size.
  - Don't compare a bool variable against the literal, "true",
    since a value with a logical non-false value need not be "1".
    I.e., don't write "if (seen == true) ...".  Rather, write "if (seen)...".