diff --git a/ChangeLog b/ChangeLog
index a0547b557227829c8b8827372c1649fc86330289..eb6347968bca696b7d0d5d827c494fd3b03cc0e3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,8 @@
 	Portability fixes.
 	* doc/Makefile.am (check-doc): Use "diff -c" instead of "diff -u"
 	for increased portability.
+	* HACKING: Use bison 1.35.  Bison 1.28 produces a file that fails
+	on AIX.
 
 	Fix Texinfo error.
 	* doc/Makefile.am (protocol-a.texi): Use '@"a', not '@"a{}', when